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  • Union,Except and Intersect operator in Linq

    - by Jalpesh P. Vadgama
    While developing a windows service using Linq-To-SQL i was in need of something that will intersect the two list and return a list with the result. After searching on net i have found three great use full operators in Linq Union,Except and Intersect. Here are explanation of each operator. Union Operator: Union operator will combine elements of both entity and return result as third new entities. Except Operator: Except operator will remove elements of first entities which elements are there in second entities and will return as third new entities. Intersect Operator: As name suggest it will return common elements of both entities and return result as new entities. Let’s take a simple console application as  a example where i have used two string array and applied the three operator one by one and print the result using Console.Writeline. Here is the code for that. C#, using GeSHi 1.0.8.6 using System; using System.Collections.Generic; using System.Linq; using System.Text;     namespace ConsoleApplication1 {     class Program     {         static void Main(string[] args)         {             string[] a = { "a", "b", "c", "d" };             string[] b = { "d","e","f","g"};               var UnResult = a.Union(b);             Console.WriteLine("Union Result");               foreach (string s in UnResult)             {                 Console.WriteLine(s);                          }               var ExResult = a.Except(b);             Console.WriteLine("Except Result");             foreach (string s in ExResult)             {                 Console.WriteLine(s);             }               var InResult = a.Intersect(b);             Console.WriteLine("Intersect Result");             foreach (string s in InResult)             {                 Console.WriteLine(s);             }             Console.ReadLine();                        }          } }   Parsed in 0.022 seconds at 45.54 KB/s Here is the output of console application as Expected. Hope this will help you.. Technorati Tags: Linq,Except,InterSect,Union,C#

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  • MySQL Connect Only 10 Days Away - Focus on InnoDB Sessions

    - by Bertrand Matthelié
    Time flies and MySQL Connect is only 10 days away! You can check out the full program here as well as in the September edition of the MySQL newsletter. Mat recently blogged about the MySQL Cluster sessions you’ll have the opportunity to attend, and below are those focused on InnoDB. Remember you can plan your schedule with Schedule Builder. Saturday, 1.00 pm, Room Golden Gate 3: 10 Things You Should Know About InnoDB—Calvin Sun, Oracle InnoDB is the default storage engine for Oracle’s MySQL as of MySQL Release 5.5. It provides the standard ACID-compliant transactions, row-level locking, multiversion concurrency control, and referential integrity. InnoDB also implements several innovative technologies to improve its performance and reliability. This presentation gives a brief history of InnoDB; its main features; and some recent enhancements for better performance, scalability, and availability. Saturday, 5.30 pm, Room Golden Gate 4: Demystified MySQL/InnoDB Performance Tuning—Dimitri Kravtchuk, Oracle This session covers performance tuning with MySQL and the InnoDB storage engine for MySQL and explains the main improvements made in MySQL Release 5.5 and Release 5.6. Which setting for which workload? Which value will be better for my system? How can I avoid potential bottlenecks from the beginning? Do I need a purge thread? Is it true that InnoDB doesn't need thread concurrency anymore? These and many other questions are asked by DBAs and developers. Things are changing quickly and constantly, and there is no “silver bullet.” But understanding the configuration setting’s impact is already a huge step in performance improvement. Bring your ideas and problems to share them with others—the discussion is open, just moderated by a speaker. Sunday, 10.15 am, Room Golden Gate 4: Better Availability with InnoDB Online Operations—Calvin Sun, Oracle Many top Web properties rely on Oracle’s MySQL as a critical piece of infrastructure for serving millions of users. Database availability has become increasingly important. One way to enhance availability is to give users full access to the database during data definition language (DDL) operations. The online DDL operations in recent MySQL releases offer users the flexibility to perform schema changes while having full access to the database—that is, with minimal delay of operations on a table and without rebuilding the entire table. These enhancements provide better responsiveness and availability in busy production environments. This session covers these improvements in the InnoDB storage engine for MySQL for online DDL operations such as add index, drop foreign key, and rename column. Sunday, 11.45 am, Room Golden Gate 7: Developing High-Throughput Services with NoSQL APIs to InnoDB and MySQL Cluster—Andrew Morgan and John Duncan, Oracle Ever-increasing performance demands of Web-based services have generated significant interest in providing NoSQL access methods to MySQL (MySQL Cluster and the InnoDB storage engine of MySQL), enabling users to maintain all the advantages of their existing relational databases while providing blazing-fast performance for simple queries. Get the best of both worlds: persistence; consistency; rich SQL queries; high availability; scalability; and simple, flexible APIs and schemas for agile development. This session describes the memcached connectors and examines some use cases for how MySQL and memcached fit together in application architectures. It does the same for the newest MySQL Cluster native connector, an easy-to-use, fully asynchronous connector for Node.js. Sunday, 1.15 pm, Room Golden Gate 4: InnoDB Performance Tuning—Inaam Rana, Oracle The InnoDB storage engine has always been highly efficient and includes many unique architectural elements to ensure high performance and scalability. In MySQL 5.5 and MySQL 5.6, InnoDB includes many new features that take better advantage of recent advances in operating systems and hardware platforms than previous releases did. This session describes unique InnoDB architectural elements for performance, new features, and how to tune InnoDB to achieve better performance. Sunday, 4.15 pm, Room Golden Gate 3: InnoDB Compression for OLTP—Nizameddin Ordulu, Facebook and Inaam Rana, Oracle Data compression is an important capability of the InnoDB storage engine for Oracle’s MySQL. Compressed tables reduce the size of the database on disk, resulting in fewer reads and writes and better throughput by reducing the I/O workload. Facebook pushes the limit of InnoDB compression and has made several enhancements to InnoDB, making this technology ready for online transaction processing (OLTP). In this session, you will learn the fundamentals of InnoDB compression. You will also learn the enhancements the Facebook team has made to improve InnoDB compression, such as reducing compression failures, not logging compressed page images, and allowing changes of compression level. Not registered yet? You can still save US$ 300 over the on-site fee – Register Now!

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  • SQLAuthority News – 7th Anniversary of Blog – A Personal Note

    - by Pinal Dave
    Special Day Today is a very special day – seven years ago I blogged for the very first time.  Seven years ago, I didn’t know what I was doing, I didn’t know how to blog, or even what a blog was or what to write.  I was working as a DBA, and I was trying to solve a problem – at my job, there were a few issues I had to fix again and again and again.  There were days when I was rewriting the same solution over and over, and there were times when I would get very frustrated because I could not write the same elegant solution that I had written before.  I came up with a solution to this problem – posting these solutions online, where I could access them whenever I needed them.  At that point, I had no idea what a blog was, or even how the internet worked, I had no idea that a blog would be visible to others.  Can you believe it? Google it on Yahoo! After a few posts on this “blog,” there was a surprise for me – an e-mail saying that someone had left me a comment.  I was surprised, because I didn’t even know you could comment on a blog!  I logged on and read my comment.  It said: “I like your script,but there is a small bug.  If you could fix it, it will run on multiple other versions of SQL Server.”  I was like, “wow, someone figured out how to find my blog, and they figured out how to fix my script!”  I found the bug, I fixed the script, and a wrote a thank you note to the guy.  My first question for him was: how did you figure it out – not the script, but how to find my blog?  He said he found it from Yahoo Search (this was in the time before Google, believe it or not). From that day, my life changed.  I wrote a few more posts, I got a few more comments, and I started to watch my traffic.  People were reading, commenting, and giving feedback.  At the end of the day, people enjoyed what I was writing.  This was a fantastic feeling!  I never thought I would be writing for others.  Even today, I don’t feel like I am writing for others, but that I am simply posting what I am learning every day.  From that very first day, I decided that I would not change my intent or my blog’s purpose. 72 Million Views – 2600 Posts – 57000 comments – 10 books – 9 courses Today, this blog is my habit, my addiction, my baby.  Every day I try to learn something new, and that lesson gets posted on the blog.  Lately there have been days where I am traveling for a full 24 hours, but even on those days I try to learn something new, and later when I have free time, I will still post it to the blog.  Because of this habit, this blog has over 72 millions views, I have written more than 2600 posts, and there are 57,000 comments and counting.  I have also written 10 books, 9 courses, and learned so many things.  This blog has given me back so much more than I ever put it into it.  It gave me an education, a reason to learn something new every day, and a way to connect to people.  I like to think of it as a learning chain, a relay where we all pass knowledge from one to another. Never Ending Journey When I started the blog, I thought I would write for a few days and stop, but now after seven years I haven’t stopped and I have no intention of stopping!  However, change happens, and for this blog it will start today.  This blog started as a single resource for SQL Server, but now it has grown beyond, to Sharepoint, Personal Development, Developer Training, MySQL, Big Data, and lots of other things.  Truly speaking, this blog is more than just SQL Server, and that was always my intention.  I named it “SQL Authority,” not “SQL Server Authority”!  Loudly and clearly, I would like to announce that I am going to go back to my roots and start writing more about SQL, more about big data, and more about the other technology like relational databases, MySQL, Oracle, and others.  My goal is not to become a comprehensive resource for every technology, my goal is to learn something new every day – and now it can be so much more than just SQL Server.  I will learn it, and post it here for you. I have written a very long post on this anniversary, but here is the summary: Thank You.  You all have been wonderful.  Seven years is a long journey, and it makes me emotional.  I have been “with” this blog before I met my wife, before we had our daughter.  This blog is like a fourth member of the family.  Keep reading, keep commenting, keep supporting.  Thank you all. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: About Me, MySQL, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL

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  • NoSQL Java API for MySQL Cluster: Questions & Answers

    - by Mat Keep
    The MySQL Cluster engineering team recently ran a live webinar, available now on-demand demonstrating the ClusterJ and ClusterJPA NoSQL APIs for MySQL Cluster, and how these can be used in building real-time, high scale Java-based services that require continuous availability. Attendees asked a number of great questions during the webinar, and I thought it would be useful to share those here, so others are also able to learn more about the Java NoSQL APIs. First, a little bit about why we developed these APIs and why they are interesting to Java developers. ClusterJ and Cluster JPA ClusterJ is a Java interface to MySQL Cluster that provides either a static or dynamic domain object model, similar to the data model used by JDO, JPA, and Hibernate. A simple API gives users extremely high performance for common operations: insert, delete, update, and query. ClusterJPA works with ClusterJ to extend functionality, including - Persistent classes - Relationships - Joins in queries - Lazy loading - Table and index creation from object model By eliminating data transformations via SQL, users get lower data access latency and higher throughput. In addition, Java developers have a more natural programming method to directly manage their data, with a complete, feature-rich solution for Object/Relational Mapping. As a result, the development of Java applications is simplified with faster development cycles resulting in accelerated time to market for new services. MySQL Cluster offers multiple NoSQL APIs alongside Java: - Memcached for a persistent, high performance, write-scalable Key/Value store, - HTTP/REST via an Apache module - C++ via the NDB API for the lowest absolute latency. Developers can use SQL as well as NoSQL APIs for access to the same data set via multiple query patterns – from simple Primary Key lookups or inserts to complex cross-shard JOINs using Adaptive Query Localization Marrying NoSQL and SQL access to an ACID-compliant database offers developers a number of benefits. MySQL Cluster’s distributed, shared-nothing architecture with auto-sharding and real time performance makes it a great fit for workloads requiring high volume OLTP. Users also get the added flexibility of being able to run real-time analytics across the same OLTP data set for real-time business insight. OK – hopefully you now have a better idea of why ClusterJ and JPA are available. Now, for the Q&A. Q & A Q. Why would I use Connector/J vs. ClusterJ? A. Partly it's a question of whether you prefer to work with SQL (Connector/J) or objects (ClusterJ). Performance of ClusterJ will be better as there is no need to pass through the MySQL Server. A ClusterJ operation can only act on a single table (e.g. no joins) - ClusterJPA extends that capability Q. Can I mix different APIs (ie ClusterJ, Connector/J) in our application for different query types? A. Yes. You can mix and match all of the API types, SQL, JDBC, ODBC, ClusterJ, Memcached, REST, C++. They all access the exact same data in the data nodes. Update through one API and new data is instantly visible to all of the others. Q. How many TCP connections would a SessionFactory instance create for a cluster of 8 data nodes? A. SessionFactory has a connection to the mgmd (management node) but otherwise is just a vehicle to create Sessions. Without using connection pooling, a SessionFactory will have one connection open with each data node. Using optional connection pooling allows multiple connections from the SessionFactory to increase throughput. Q. Can you give details of how Cluster J optimizes sharding to enhance performance of distributed query processing? A. Each data node in a cluster runs a Transaction Coordinator (TC), which begins and ends the transaction, but also serves as a resource to operate on the result rows. While an API node (such as a ClusterJ process) can send queries to any TC/data node, there are performance gains if the TC is where most of the result data is stored. ClusterJ computes the shard (partition) key to choose the data node where the row resides as the TC. Q. What happens if we perform two primary key lookups within the same transaction? Are they sent to the data node in one transaction? A. ClusterJ will send identical PK lookups to the same data node. Q. How is distributed query processing handled by MySQL Cluster ? A. If the data is split between data nodes then all of the information will be transparently combined and passed back to the application. The session will connect to a data node - typically by hashing the primary key - which then interacts with its neighboring nodes to collect the data needed to fulfil the query. Q. Can I use Foreign Keys with MySQL Cluster A. Support for Foreign Keys is included in the MySQL Cluster 7.3 Early Access release Summary The NoSQL Java APIs are packaged with MySQL Cluster, available for download here so feel free to take them for a spin today! Key Resources MySQL Cluster on-line demo  MySQL ClusterJ and JPA On-demand webinar  MySQL ClusterJ and JPA documentation MySQL ClusterJ and JPA whitepaper and tutorial

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  • Windows Azure Recipe: Software as a Service (SaaS)

    - by Clint Edmonson
    The cloud was tailor built for aspiring companies to create innovative internet based applications and solutions. Whether you’re a garage startup with very little capital or a Fortune 1000 company, the ability to quickly setup, deliver, and iterate on new products is key to capturing market and mind share. And if you can capture that share and go viral, having resiliency and infinite scale at your finger tips is great peace of mind. Drivers Cost avoidance Time to market Scalability Solution Here’s a sketch of how a basic Software as a Service solution might be built out: Ingredients Web Role – this hosts the core web application. Each web role will host an instance of the software and as the user base grows, additional roles can be spun up to meet demand. Access Control – this service is essential to managing user identity. It’s backed by a full blown implementation of Active Directory and allows the definition and management of users, groups, and roles. A pre-built ASP.NET membership provider is included in the training kit to leverage this capability but it’s also flexible enough to be combined with external Identity providers including Windows LiveID, Google, Yahoo!, and Facebook. The provider model provides extensibility to hook into other industry specific identity providers as well. Databases – nearly every modern SaaS application is backed by a relational database for its core operational data. If the solution is sold to organizations, there’s a good chance multi-tenancy will be needed. An emerging best practice for SaaS applications is to stand up separate SQL Azure database instances for each tenant’s proprietary data to ensure isolation from other tenants. Worker Role – this is the best place to handle autonomous background processing such as data aggregation, billing through external services, and other specialized tasks that can be performed asynchronously. Placing these tasks in a worker role frees the web roles to focus completely on user interaction and data input and provides finer grained control over the system’s scalability and throughput. Caching (optional) – as a web site traffic grows caching can be leveraged to keep frequently used read-only, user specific, and application resource data in a high-speed distributed in-memory for faster response times and ultimately higher scalability without spinning up more web and worker roles. It includes a token based security model that works alongside the Access Control service. Blobs (optional) – depending on the nature of the software, users may be creating or uploading large volumes of heterogeneous data such as documents or rich media. Blob storage provides a scalable, resilient way to store terabytes of user data. The storage facilities can also integrate with the Access Control service to ensure users’ data is delivered securely. Training & Examples These links point to online Windows Azure training labs and examples where you can learn more about the individual ingredients described above. (Note: The entire Windows Azure Training Kit can also be downloaded for offline use.) Windows Azure (16 labs) Windows Azure is an internet-scale cloud computing and services platform hosted in Microsoft data centers, which provides an operating system and a set of developer services which can be used individually or together. It gives developers the choice to build web applications; applications running on connected devices, PCs, or servers; or hybrid solutions offering the best of both worlds. New or enhanced applications can be built using existing skills with the Visual Studio development environment and the .NET Framework. With its standards-based and interoperable approach, the services platform supports multiple internet protocols, including HTTP, REST, SOAP, and plain XML SQL Azure (7 labs) Microsoft SQL Azure delivers on the Microsoft Data Platform vision of extending the SQL Server capabilities to the cloud as web-based services, enabling you to store structured, semi-structured, and unstructured data. Windows Azure Services (9 labs) As applications collaborate across organizational boundaries, ensuring secure transactions across disparate security domains is crucial but difficult to implement. Windows Azure Services provides hosted authentication and access control using powerful, secure, standards-based infrastructure. Developing Applications for the Cloud, 2nd Edition (eBook) This book demonstrates how you can create from scratch a multi-tenant, Software as a Service (SaaS) application to run in the cloud using the latest versions of the Windows Azure Platform and tools. The book is intended for any architect, developer, or information technology (IT) professional who designs, builds, or operates applications and services that run on or interact with the cloud. Fabrikam Shipping (SaaS reference application) This is a full end to end sample scenario which demonstrates how to use the Windows Azure platform for exposing an application as a service. We developed this demo just as you would: we had an existing on-premises sample, Fabrikam Shipping, and we wanted to see what it would take to transform it in a full subscription based solution. The demo you find here is the result of that investigation See my Windows Azure Resource Guide for more guidance on how to get started, including more links web portals, training kits, samples, and blogs related to Windows Azure.

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  • Some mail details about Orange Mauritius

    Being an internet service provider is not easy after all for a lot of companies. Luckily, there are quite some good international operators in this world. For example Orange Mauritius aka Mauritius Telecom aka Wanadoo(?) aka MyT here in Mauritius. The local circumstances give them a quasi-monopol position on fixed lines for telephony and therefore cable-based DSL internet connectivity. So far, not bad but as usual... the details. Just for the records, I am only using the services of Orange for mobile but friends and customers are bound, eh stuck, with other services of Orange Mauritius. And usually, being the IT guy, they get in touch with me to complain about problems or to ask questions on either their ADSL / MyT connection, mail services or whatever. Most of those issues are user-related and easily to solve by tweaking the configuration of their computer a little bit but sometimes it's getting weird. Using Orange ADSL... somewhere else Now, let's imagine we are an Orange ADSL customer for ages and we are using their mail services with our very own mail address like "[email protected]". We configured our mail client like Thunderbird, Outlook Express, Outlook or Windows Mail as publicly described, and we are able to receive and send emails like a champion. No problems at all, the world is green. Did I mention that we have a laptop? Ok, let's take our movable piece of information technology and visit a friend here on the island. Not surprising, he is also customer of Orange, so we can read and answer emails. But Orange is not the online internet service provider and one day, we happen to hang out with someone that uses Emtel via WiMAX or UMTS.. And the fun starts... We can still receive and read emails from our Orange mail account and the IT world is still bright but try to send mails to someone outside the domain "@intnet.mu" or "@orange.mu". Your mail client will deny sending mail with SMTP message 5.1.0 "blah not allowed". First guess, there is problem with the mail client, maybe magically the configuration changed over-night. But no it is still working at home... So, there is for sure a problem with the guy's internet connection. At least, it is his fault not to have Orange internet services, so it can not work properly... The Orange Mail FAQ After some more frustation we finally checkout the Orange Mail FAQ to see whether this (obviously?) common problem has been described already. Sorry, but those FAQ entries are even more confusing as it is not really clear how to handle this scenario. Best of all is that most of the entries are still refering to use servers of the domain "intnet.mu". I mean Orange will disable those systems in favour of the domain "orange.mu" in the near future and does not amend their FAQs. Come on, guys! Ok, settings for POP3 are there. Hm, what about the secure version POP3S? No signs at all... Even changing your mail client to use password encryption with STARTTLS is not allowed at all. Use "bow.intnet.mu" for incoming mail... Ahhh, pretty obvious host name. I mean, at least something like pop.intnet.mu or pop3.intnet.mu would have been more accurate. Funny of all, the hostname "pop.orange.mu" is accessible to receive your mail account. Alright, checking SMTP options for authentication or other like POP-before-SMTP or whatever well-known and established mechanism to send emails are described. I guess that spotting a whale or shark in Mauritian waters would be easier. Trial and error on SMTP settings reveal that neither STARTTLS or any other connection / password encryption is available. Using SSL/TLS on SMTP only reveals that there is no service answering your request. Calling customer service So, we have to bite into the bitter apple and get in touch with Orange customer service and complain/explain them our case and ask for advice. After some hiccups, we finally manage to get hold of someone competent in mail services and we receive the golden spoon of mail configuration made by Orange Mauritius: SMTP hostname: smtpauth.intnet.mu And the world of IT is surprisingly green again. Customer satisfaction? Dear Orange Mauritius, what's the problem with this information? Are you scared of mail spammer? Why isn't there any case in your FAQs? Ok, talking about your FAQs - simply said: they are badly outdated! Configure your mail client to use server name based in the domain intnet.mu but specify your account username with orange.mu as domain part. Although, that there are servers available on the domain orange.mu after all. So, why don't you provide current information like this: POP3 server name: pop.orange.muSMTP server name: smtp.orange.muSMTP authenticated: smtpauth.orange.mu It's not difficult, is it? In my humble opinion not really and you would provide clean, consistent and up-to-date information for your customers. This would produce less frustation and so less traffic on your customer service lines. Which after all, would improve the total user experience and satisfaction level on both sides. Without knowing these facts. Now, imagine you would take your laptop abroad and have to use other internet service providers to be able to be online... Calling your customer service would be unnecessary expensive!

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  • Closing the gap between strategy and execution with Oracle Business Intelligence 11g

    - by manan.goel(at)oracle.com
    Wikipedia defines strategy as a plan of action designed to achieve a particular goal. An example of this is General Electric's acquisitions and divestiture strategy (plan) designed to propel GE to number 1 or 2 place (goal) in every business segment that it operated in. Execution on the other hand can be defined as the actions taken to getting things done. In GE's case execution will be steps followed for mergers/acquisitions or divestiture. Business press has written extensively about the importance of both strategy and execution in achieving desired business objectives. Perhaps the quote from Thomas Edison says it best - "vision without execution is hallucination". Conversely, it can be said that "execution without vision" is well may be "wishful thinking". Research overwhelmingly point towards the wide gap between strategy and execution. According to a published study, 49% of surveyed executives perceive a gap between their organizations' ability to develop and communicate sound strategies and their ability to implement those strategies. Further, of these respondents, 64% don't have full confidence that their companies will be able to close the gap. Having established the severity and importance of the problem let's talk about the reasons for the strategy-execution gap. The common reasons include: -        Lack of clearly defined goals -        Lack of consistent measure of success -        Lack of ownership -        Lack of alignment -        Lack of communication -        Lack of proper execution -        Lack of monitoring       There are multiple approaches to solving the problem including organizational development practices, technology enablement etc. In most cases a combination of approaches is required to achieve the desired result. For the purposes of this discussion, I'll focus on technology.  Imagine an integrated closed loop technology platform that automates the entire management cycle from defining strategy to assigning ownership to communicating goals to achieving alignment to collaboration to taking actions to monitoring progress and achieving mid course corrections. Besides, for best ROI and lowest TCO such a system should also have characteristics like:  Complete -        Full functionality -        Rich end user access Open -        Any data source -        Any business application -        Any technology stack  Integrated -        Common metadata -        Common security -        Common system management From a capabilities perspective the system should provide the following capabilities: Define -        Strategy -        Objectives -        Ownership -        KPI's Communicate -        Pervasive -        Collaborative -        Role based -        Secure Execute -        Integrated -        Intuitive -        Secure -        Ubiquitous Monitor -        Multiple styles and formats -        Exception based -        Push & Pull Having talked about the business problem and outlined the blueprint for a technology solution, let's talk about how Oracle Business Intelligence 11g can help. Oracle Business Intelligence is a comprehensive business intelligence solution for reporting, ad hoc query and analysis, OLAP, dashboards and scorecards. Oracle's best in class BI platform is based on an architecturally integrated technology foundation that provides a unified end user experience and features a Common Enterprise Information Model, with common security, query request generation and optimization, and system management. The BI platform is ·         Complete - meaning it delivers all modes and styles of BI including reporting, ad hoc query and analysis, OLAP, dashboards and scorecards with a rich end user experience that includes visualization, collaboration, alerts and notifications, search and mobile access. ·         Open - meaning the BI platform integrates with any data source, ETL tool, business application, application server, security infrastructure, portal technology as well as any ODBC compliant third party analytical tool. The suite accesses data from multiple heterogeneous sources--including popular relational and multidimensional data sources and major ERP and CRM applications from Oracle and SAP. ·         Integrated - meaning the BI platform is based on an architecturally integrated technology foundation built on an open, standards based service oriented architecture.  The platform features a common enterprise information model, common security model and a common configuration, deployment and systems management framework. To summarize, Oracle Business Intelligence is a comprehensive, integrated BI platform that lets you define strategy, identify objectives, assign ownership, define KPI's, collaborate, take action, monitor, report and do course corrections all form a single interface and a single system. The platform's integrated metadata model and task based design ensures that the entire workflow from defining strategy to execution to monitoring is completely integrated delivering end to end visibility, transparency and agility. Click here to learn more about Oracle BI 11g. 

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  • ODI 12c - Aggregating Data

    - by David Allan
    This posting will look at the aggregation component that was introduced in ODI 12c. For many ETL tool users this shouldn't be a big surprise, its a little different than ODI 11g but for good reason. You can use this component for composing data with relational like operations such as sum, average and so forth. Also, Oracle SQL supports special functions called Analytic SQL functions, you can use a specially configured aggregation component or the expression component for these now in ODI 12c. In database systems an aggregate transformation is a transformation where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning - that's exactly the purpose of the aggregate component. In the image below you can see the aggregate component in action within a mapping, for how this and a few other examples are built look at the ODI 12c Aggregation Viewlet here - the viewlet illustrates a simple aggregation being built and then some Oracle analytic SQL such as AVG(EMP.SAL) OVER (PARTITION BY EMP.DEPTNO) built using both the aggregate component and the expression component. In 11g you used to just write the aggregate expression directly on the target, this made life easy for some cases, but it wan't a very obvious gesture plus had other drawbacks with ordering of transformations (agg before join/lookup. after set and so forth) and supporting analytic SQL for example - there are a lot of postings from creative folks working around this in 11g - anything from customizing KMs, to bypassing aggregation analysis in the ODI code generator. The aggregate component has a few interesting aspects. 1. Firstly and foremost it defines the attributes projected from it - ODI automatically will perform the grouping all you do is define the aggregation expressions for those columns aggregated. In 12c you can control this automatic grouping behavior so that you get the code you desire, so you can indicate that an attribute should not be included in the group by, that's what I did in the analytic SQL example using the aggregate component. 2. The component has a few other properties of interest; it has a HAVING clause and a manual group by clause. The HAVING clause includes a predicate used to filter rows resulting from the GROUP BY clause. Because it acts on the results of the GROUP BY clause, aggregation functions can be used in the HAVING clause predicate, in 11g the filter was overloaded and used for both having clause and filter clause, this is no longer the case. If a filter is after an aggregate, it is after the aggregate (not sometimes after, sometimes having).  3. The manual group by clause let's you use special database grouping grammar if you need to. For example Oracle has a wealth of highly specialized grouping capabilities for data warehousing such as the CUBE function. If you want to use specialized functions like that you can manually define the code here. The example below shows the use of a manual group from an example in the Oracle database data warehousing guide where the SUM aggregate function is used along with the CUBE function in the group by clause. The SQL I am trying to generate looks like the following from the data warehousing guide; SELECT channel_desc, calendar_month_desc, countries.country_iso_code,       TO_CHAR(SUM(amount_sold), '9,999,999,999') SALES$ FROM sales, customers, times, channels, countries WHERE sales.time_id=times.time_id AND sales.cust_id=customers.cust_id AND   sales.channel_id= channels.channel_id  AND customers.country_id = countries.country_id  AND channels.channel_desc IN   ('Direct Sales', 'Internet') AND times.calendar_month_desc IN   ('2000-09', '2000-10') AND countries.country_iso_code IN ('GB', 'US') GROUP BY CUBE(channel_desc, calendar_month_desc, countries.country_iso_code); I can capture the source datastores, the filters and joins using ODI's dataset (or as a traditional flow) which enables us to incrementally design the mapping and the aggregate component for the sum and group by as follows; In the above mapping you can see the joins and filters declared in ODI's dataset, allowing you to capture the relationships of the datastores required in an entity-relationship style just like ODI 11g. The mix of ODI's declarative design and the common flow design provides for a familiar design experience. The example below illustrates flow design (basic arbitrary ordering) - a table load where only the employees who have maximum commission are loaded into a target. The maximum commission is retrieved from the bonus datastore and there is a look using employees as the driving table and only those with maximum commission projected. Hopefully this has given you a taster for some of the new capabilities provided by the aggregate component in ODI 12c. In summary, the actions should be much more consistent in behavior and more easily discoverable for users, the use of the components in a flow graph also supports arbitrary designs and the tool (rather than the interface designer) takes care of the realization using ODI's knowledge modules. Interested to know if a deep dive into each component is interesting for folks. Any thoughts? 

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  • Big Data – Buzz Words: What is HDFS – Day 8 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is MapReduce. In this article we will take a quick look at one of the four most important buzz words which goes around Big Data – HDFS. What is HDFS ? HDFS stands for Hadoop Distributed File System and it is a primary storage system used by Hadoop. It provides high performance access to data across Hadoop clusters. It is usually deployed on low-cost commodity hardware. In commodity hardware deployment server failures are very common. Due to the same reason HDFS is built to have high fault tolerance. The data transfer rate between compute nodes in HDFS is very high, which leads to reduced risk of failure. HDFS creates smaller pieces of the big data and distributes it on different nodes. It also copies each smaller piece to multiple times on different nodes. Hence when any node with the data crashes the system is automatically able to use the data from a different node and continue the process. This is the key feature of the HDFS system. Architecture of HDFS The architecture of the HDFS is master/slave architecture. An HDFS cluster always consists of single NameNode. This single NameNode is a master server and it manages the file system as well regulates access to various files. In additional to NameNode there are multiple DataNodes. There is always one DataNode for each data server. In HDFS a big file is split into one or more blocks and those blocks are stored in a set of DataNodes. The primary task of the NameNode is to open, close or rename files and directory and regulate access to the file system, whereas the primary task of the DataNode is read and write to the file systems. DataNode is also responsible for the creation, deletion or replication of the data based on the instruction from NameNode. In reality, NameNode and DataNode are software designed to run on commodity machine build in Java language. Visual Representation of HDFS Architecture Let us understand how HDFS works with the help of the diagram. Client APP or HDFS Client connects to NameSpace as well as DataNode. Client App access to the DataNode is regulated by NameSpace Node. NameSpace Node allows Client App to connect to the DataNode based by allowing the connection to the DataNode directly. A big data file is divided into multiple data blocks (let us assume that those data chunks are A,B,C and D. Client App will later on write data blocks directly to the DataNode. Client App does not have to directly write to all the node. It just has to write to any one of the node and NameNode will decide on which other DataNode it will have to replicate the data. In our example Client App directly writes to DataNode 1 and detained 3. However, data chunks are automatically replicated to other nodes. All the information like in which DataNode which data block is placed is written back to NameNode. High Availability During Disaster Now as multiple DataNode have same data blocks in the case of any DataNode which faces the disaster, the entire process will continue as other DataNode will assume the role to serve the specific data block which was on the failed node. This system provides very high tolerance to disaster and provides high availability. If you notice there is only single NameNode in our architecture. If that node fails our entire Hadoop Application will stop performing as it is a single node where we store all the metadata. As this node is very critical, it is usually replicated on another clustered as well as on another data rack. Though, that replicated node is not operational in architecture, it has all the necessary data to perform the task of the NameNode in the case of the NameNode fails. The entire Hadoop architecture is built to function smoothly even there are node failures or hardware malfunction. It is built on the simple concept that data is so big it is impossible to have come up with a single piece of the hardware which can manage it properly. We need lots of commodity (cheap) hardware to manage our big data and hardware failure is part of the commodity servers. To reduce the impact of hardware failure Hadoop architecture is built to overcome the limitation of the non-functioning hardware. Tomorrow In tomorrow’s blog post we will discuss the importance of the relational database in Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • When is my View too smart?

    - by Kyle Burns
    In this posting, I will discuss the motivation behind keeping View code as thin as possible when using patterns such as MVC, MVVM, and MVP.  Once the motivation is identified, I will examine some ways to determine whether a View contains logic that belongs in another part of the application.  While the concepts that I will discuss are applicable to most any pattern which favors a thin View, any concrete examples that I present will center on ASP.NET MVC. Design patterns that include a Model, a View, and other components such as a Controller, ViewModel, or Presenter are not new to application development.  These patterns have, in fact, been around since the early days of building applications with graphical interfaces.  The reason that these patterns emerged is simple – the code running closest to the user tends to be littered with logic and library calls that center around implementation details of showing and manipulating user interface widgets and when this type of code is interspersed with application domain logic it becomes difficult to understand and much more difficult to adequately test.  By removing domain logic from the View, we ensure that the View has a single responsibility of drawing the screen which, in turn, makes our application easier to understand and maintain. I was recently asked to take a look at an ASP.NET MVC View because the developer reviewing it thought that it possibly had too much going on in the view.  I looked at the .CSHTML file and the first thing that occurred to me was that it began with 40 lines of code declaring member variables and performing the necessary calculations to populate these variables, which were later either output directly to the page or used to control some conditional rendering action (such as adding a class name to an HTML element or not rendering another element at all).  This exhibited both of what I consider the primary heuristics (or code smells) indicating that the View is too smart: Member variables – in general, variables in View code are an indication that the Model to which the View is being bound is not sufficient for the needs of the View and that the View has had to augment that Model.  Notable exceptions to this guideline include variables used to hold information specifically related to rendering (such as a dynamically determined CSS class name or the depth within a recursive structure for indentation purposes) and variables which are used to facilitate looping through collections while binding. Arithmetic – as with member variables, the presence of arithmetic operators within View code are an indication that the Model servicing the View is insufficient for its needs.  For example, if the Model represents a line item in a sales order, it might seem perfectly natural to “normalize” the Model by storing the quantity and unit price in the Model and multiply these within the View to show the line total.  While this does seem natural, it introduces a business rule to the View code and makes it impossible to test that the rounding of the result meets the requirement of the business without executing the View.  Within View code, arithmetic should only be used for activities such as incrementing loop counters and calculating element widths. In addition to the two characteristics of a “Smart View” that I’ve discussed already, this View also exhibited another heuristic that commonly indicates to me the need to refactor a View and make it a bit less smart.  That characteristic is the existence of Boolean logic that either does not work directly with properties of the Model or works with too many properties of the Model.  Consider the following code and consider how logic that does not work directly with properties of the Model is just another form of the “member variable” heuristic covered earlier: @if(DateTime.Now.Hour < 12) {     <div>Good Morning!</div> } else {     <div>Greetings</div> } This code performs business logic to determine whether it is morning.  A possible refactoring would be to add an IsMorning property to the Model, but in this particular case there is enough similarity between the branches that the entire branching structure could be collapsed by adding a Greeting property to the Model and using it similarly to the following: <div>@Model.Greeting</div> Now let’s look at some complex logic around multiple Model properties: @if (ModelPageNumber + Model.NumbersToDisplay == Model.PageCount         || (Model.PageCount != Model.CurrentPage             && !Model.DisplayValues.Contains(Model.PageCount))) {     <div>There's more to see!</div> } In this scenario, not only is the View code difficult to read (you shouldn’t have to play “human compiler” to determine the purpose of the code), but it also complex enough to be at risk for logical errors that cannot be detected without executing the View.  Conditional logic that requires more than a single logical operator should be looked at more closely to determine whether the condition should be evaluated elsewhere and exposed as a single property of the Model.  Moving the logic above outside of the View and exposing a new Model property would simplify the View code to: @if(Model.HasMoreToSee) {     <div>There’s more to see!</div> } In this posting I have briefly discussed some of the more prominent heuristics that indicate a need to push code from the View into other pieces of the application.  You should now be able to recognize these symptoms when building or maintaining Views (or the Models that support them) in your applications.

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  • YouTube Scalability Lessons

    - by Bertrand Matthelié
    @font-face { font-family: "Arial"; }@font-face { font-family: "Courier New"; }@font-face { font-family: "Wingdings"; }@font-face { font-family: "Calibri"; }@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }h2 { margin: 12pt 0cm 3pt; page-break-after: avoid; font-size: 14pt; font-family: "Times New Roman"; font-style: italic; }a:link, span.MsoHyperlink { color: blue; text-decoration: underline; }a:visited, span.MsoHyperlinkFollowed { color: purple; text-decoration: underline; }span.Heading2Char { font-family: Calibri; font-weight: bold; font-style: italic; }div.Section1 { page: Section1; }ol { margin-bottom: 0cm; }ul { margin-bottom: 0cm; } Very interesting blog post by Todd Hoff at highscalability.com presenting “7 Years of YouTube Scalability Lessons in 30 min” based on a presentation from Mike Solomon, one of the original engineers at YouTube: …. The key takeaway away of the talk for me was doing a lot with really simple tools. While many teams are moving on to more complex ecosystems, YouTube really does keep it simple. They program primarily in Python, use MySQL as their database, they’ve stuck with Apache, and even new features for such a massive site start as a very simple Python program. That doesn’t mean YouTube doesn’t do cool stuff, they do, but what makes everything work together is more a philosophy or a way of doing things than technological hocus pocus. What made YouTube into one of the world’s largest websites? Read on and see... Stats @font-face { font-family: "Arial"; }@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } 4 billion Views a day 60 hours of video is uploaded every minute 350+ million devices are YouTube enabled Revenue double in 2010 The number of videos has gone up 9 orders of magnitude and the number of developers has only gone up two orders of magnitude. 1 million lines of Python code Stack @font-face { font-family: "Arial"; }@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } Python - most of the lines of code for YouTube are still in Python. Everytime you watch a YouTube video you are executing a bunch of Python code. Apache - when you think you need to get rid of it, you don’t. Apache is a real rockstar technology at YouTube because they keep it simple. Every request goes through Apache. Linux - the benefit of Linux is there’s always a way to get in and see how your system is behaving. No matter how bad your app is behaving, you can take a look at it with Linux tools like strace and tcpdump. MySQL - is used a lot. When you watch a video you are getting data from MySQL. Sometime it’s used a relational database or a blob store. It’s about tuning and making choices about how you organize your data. Vitess- a  new project released by YouTube, written in Go, it’s a frontend to MySQL. It does a lot of optimization on the fly, it rewrites queries and acts as a proxy. Currently it serves every YouTube database request. It’s RPC based. Zookeeper - a distributed lock server. It’s used for configuration. Really interesting piece of technology. Hard to use correctly so read the manual Wiseguy - a CGI servlet container. Spitfire - a templating system. It has an abstract syntax tree that let’s them do transformations to make things go faster. Serialization formats - no matter which one you use, they are all expensive. Measure. Don’t use pickle. Not a good choice. Found protocol buffers slow. They wrote their own BSON implementation, which is 10-15 time faster than the one you can download. ...Contiues. Read the blog Watch the video

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  • MERGE gives better OUTPUT options

    - by Rob Farley
    MERGE is very cool. There are a ton of useful things about it – mostly around the fact that you can implement a ton of change against a table all at once. This is great for data warehousing, handling changes made to relational databases by applications, all kinds of things. One of the more subtle things about MERGE is the power of the OUTPUT clause. Useful for logging.   If you’re not familiar with the OUTPUT clause, you really should be – it basically makes your DML (INSERT/DELETE/UPDATE/MERGE) statement return data back to you. This is a great way of returning identity values from INSERT commands (so much better than SCOPE_IDENTITY() or the older (and worse) @@IDENTITY, because you can get lots of rows back). You can even use it to grab default values that are set using non-deterministic functions like NEWID() – things you couldn’t normally get back without running another query (or with a trigger, I guess, but that’s not pretty). That inserted table I referenced – that’s part of the ‘behind-the-scenes’ work that goes on with all DML changes. When you insert data, this internal table called inserted gets populated with rows, and then used to inflict the appropriate inserts on the various structures that store data (HoBTs – the Heaps or B-Trees used to store data as tables and indexes). When deleting, the deleted table gets populated. Updates get a matching row in both tables (although this doesn’t mean that an update is a delete followed by an inserted, it’s just the way it’s handled with these tables). These tables can be referenced by the OUTPUT clause, which can show you the before and after for any DML statement. Useful stuff. MERGE is slightly different though. With MERGE, you get a mix of entries. Your MERGE statement might be doing some INSERTs, some UPDATEs and some DELETEs. One of the most common examples of MERGE is to perform an UPSERT command, where data is updated if it already exists, or inserted if it’s new. And in a single operation too. Here, you can see the usefulness of the deleted and inserted tables, which clearly reflect the type of operation (but then again, MERGE lets you use an extra column called $action to show this). (Don’t worry about the fact that I turned on IDENTITY_INSERT, that’s just so that I could insert the values) One of the things I love about MERGE is that it feels almost cursor-like – the UPDATE bit feels like “WHERE CURRENT OF …”, and the INSERT bit feels like a single-row insert. And it is – but into the inserted and deleted tables. The operations to maintain the HoBTs are still done using the whole set of changes, which is very cool. And $action – very convenient. But as cool as $action is, that’s not the point of my post. If it were, I hope you’d all be disappointed, as you can’t really go near the MERGE statement without learning about it. The subtle thing that I love about MERGE with OUTPUT is that you can hook into more than just inserted and deleted. Did you notice in my earlier query that my source table had a ‘src’ field, that wasn’t used in the insert? Normally, this would be somewhat pointless to include in my source query. But with MERGE, I can put that in the OUTPUT clause. This is useful stuff, particularly when you’re needing to audit the changes. Suppose your query involved consolidating data from a number of sources, but you didn’t need to insert that into the actual table, just into a table for audit. This is now very doable, either using the INTO clause of OUTPUT, or surrounding the whole MERGE statement in brackets (parentheses if you’re American) and using a regular INSERT statement. This is also doable if you’re using MERGE to just do INSERTs. In case you hadn’t realised, you can use MERGE in place of an INSERT statement. It’s just like the UPSERT-style statement we’ve just seen, except that we want nothing to match. That’s easy to do, we just use ON 1=2. This is obviously more convoluted than a straight INSERT. And it’s slightly more effort for the database engine too. But, if you want the extra audit capabilities, the ability to hook into the other source columns is definitely useful. Oh, and before people ask if you can also hook into the target table’s columns... Yes, of course. That’s what deleted and inserted give you.

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  • What Counts For a DBA: Fitness

    - by Louis Davidson
    If you know me, you can probably guess that physical exercise is not really my thing. There was a time in my past when it a larger part of my life, but even then never in the same sort of passionate way as a number of our SQL friends.  For me, I find that mental exercise satisfies what I believe to be the same inner need that drives people to run farther than I like to drive on most Saturday mornings, and it is certainly just as addictive. Mental fitness shares many common traits with physical fitness, especially the need to attain it through repetitive training. I only wish that mental training burned off a bacon cheeseburger in the same manner as does jogging around a dewy park on Saturday morning. In physical training, there are at least two goals, the first of which is to be physically able to do a task. The second is to train the brain to perform the task without thinking too hard about it. No matter how long it has been since you last rode a bike, you will be almost certainly be able to hop on and start riding without thinking about the process of pedaling or balancing. If you’ve never ridden a bike, you could be a physics professor /Olympic athlete and still crash the first few times you try, even though you are as strong as an ox and your knowledge of the physics of bicycle riding makes the concept child’s play. For programming tasks, the process is very similar. As a DBA, you will come to know intuitively how to backup, optimize, and secure database systems. As a data programmer, you will work to instinctively use the clauses of Transact-SQL DML so that, when you need to group data three ways (and not four), you will know to use the GROUP BY clause with GROUPING SETS without resorting to a search engine.  You have the skill. Making it naturally then requires repetition and experience is the primary requirement, not just simply learning about a topic. The hardest part of being really good at something is this difference between knowledge and skill. I have recently taken several informative training classes with Kimball University on data warehousing and ETL. Now I have a lot more knowledge about designing data warehouses than before. I have also done a good bit of data warehouse designing of late and have started to improve to some level of proficiency with the theory. Yet, for all of this head knowledge, it is still a struggle to take what I have learned and apply it to the designs I am working on.  Data warehousing is still a task that is not yet deeply ingrained in my brain muscle memory. On the other hand, relational database design is something that no matter how much or how little I may get to do it, I am comfortable doing it. I have done it as a profession now for well over a decade, I teach classes on it, and I also have done (and continue to do) a lot of mental training beyond the work day. Sometimes the training is just basic education, some reading blogs and attending sessions at PASS events.  My best training comes from spending time working on other people’s design issues in forums (though not nearly as much as I would like to lately). Working through other people’s problems is a great way to exercise your brain on problems with which you’re not immediately familiar. The final bit of exercise I find useful for cultivating mental fitness for a data professional is also probably the nerdiest thing that I will ever suggest you do.  Akin to running in place, the idea is to work through designs in your head. I have designed more than one database system that would revolutionize grocery store operations, sales at my local Target store, the ordering process at Amazon, and ways to improve Disney World operations to get me through a line faster (some of which they are starting to implement without any of my help.) Never are the designs truly fleshed out, but enough to work through structures and processes.  On “paper”, I have designed database systems to catalog things as trivial as my Lego creations, rental car companies and my audio and video collections. Once I get the database designed mentally, sometimes I will create the database, add some data (often using Red-Gate’s Data Generator), and write a few queries to see if a concept was realistic, but I will rarely fully flesh out the database since I have no desire to do any user interface programming anymore.  The mental training allows me to keep in practice for when the time comes to do the work I love the most for real…even if I have been spending most of my work time lately building data warehouses.  If you are really strong of mind and body, perhaps you can mix a mental run with a physical run; though don’t run off of a cliff while contemplating how you might design a database to catalog the trees on a mountain…that would be contradictory to the purpose of both types of exercise.

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  • How to get distinct values from the List&lt;T&gt; with LINQ

    - by Vincent Maverick Durano
    Recently I was working with data from a generic List<T> and one of my objectives is to get the distinct values that is found in the List. Consider that we have this simple class that holds the following properties: public class Product { public string Make { get; set; } public string Model { get; set; } }   Now in the page code behind we will create a list of product by doing the following: private List<Product> GetProducts() { List<Product> products = new List<Product>(); Product p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy S 1"; products.Add(p); p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy S 2"; products.Add(p); p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy Note"; products.Add(p); p = new Product(); p.Make = "Apple"; p.Model = "iPhone 4"; products.Add(p); p = new Product(); p.Make = "Apple"; p.Model = "iPhone 4s"; products.Add(p); p = new Product(); p.Make = "HTC"; p.Model = "Sensation"; products.Add(p); p = new Product(); p.Make = "HTC"; p.Model = "Desire"; products.Add(p); p = new Product(); p.Make = "Nokia"; p.Model = "Some Model"; products.Add(p); p = new Product(); p.Make = "Nokia"; p.Model = "Some Model"; products.Add(p); p = new Product(); p.Make = "Sony Ericsson"; p.Model = "800i"; products.Add(p); p = new Product(); p.Make = "Sony Ericsson"; p.Model = "800i"; products.Add(p); return products; }   And then let’s bind the products to the GridView. protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Gridview1.DataSource = GetProducts(); Gridview1.DataBind(); } }   Running the code will display something like this in the page: Now what I want is to get the distinct row values from the list. So what I did is to use the LINQ Distinct operator and unfortunately it doesn't work. In order for it work is you must use the overload method of the Distinct operator for you to get the desired results. So I’ve added this IEqualityComparer<T> class to compare values: class ProductComparer : IEqualityComparer<Product> { public bool Equals(Product x, Product y) { if (Object.ReferenceEquals(x, y)) return true; if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null)) return false; return x.Make == y.Make && x.Model == y.Model; } public int GetHashCode(Product product) { if (Object.ReferenceEquals(product, null)) return 0; int hashProductName = product.Make == null ? 0 : product.Make.GetHashCode(); int hashProductCode = product.Model.GetHashCode(); return hashProductName ^ hashProductCode; } }   After that you can then bind the GridView like this: protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Gridview1.DataSource = GetProducts().Distinct(new ProductComparer()); Gridview1.DataBind(); } }   Running the page will give you the desired output below: As you notice, it now eliminates the duplicate rows in the GridView. Now what if we only want to get the distinct values for a certain field. For example I want to get the distinct “Make” values such as Samsung, Apple, HTC, Nokia and Sony Ericsson and populate them to a DropDownList control for filtering purposes. I was hoping the the Distinct operator has an overload that can compare values based on the property value like (GetProducts().Distinct(o => o.PropertyToCompare). But unfortunately it doesn’t provide that overload so what I did as a workaround is to use the GroupBy,Select and First LINQ query operators to achieve what I want. Here’s the code to get the distinct values of a certain field. protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { DropDownList1.DataSource = GetProducts().GroupBy(o => o.Make).Select(o => o.First()); DropDownList1.DataTextField = "Make"; DropDownList1.DataValueField = "Model"; DropDownList1.DataBind(); } } Running the code will display the following output below:   That’s it! I hope someone find this post useful!

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • Joining on NULLs

    - by Dave Ballantyne
    A problem I see on a fairly regular basis is that of dealing with NULL values.  Specifically here, where we are joining two tables on two columns, one of which is ‘optional’ ie is nullable.  So something like this: i.e. Lookup where all the columns are equal, even when NULL.   NULL’s are a tricky thing to initially wrap your mind around.  Statements like “NULL is not equal to NULL and neither is it not not equal to NULL, it’s NULL” can cause a serious brain freeze and leave you a gibbering wreck and needing your mummy. Before we plod on, time to setup some data to demo against. Create table #SourceTable ( Id integer not null, SubId integer null, AnotherCol char(255) not null ) go create unique clustered index idxSourceTable on #SourceTable(id,subID) go with cteNums as ( select top(1000) number from master..spt_values where type ='P' ) insert into #SourceTable select Num1.number,nullif(Num2.number,0),'SomeJunk' from cteNums num1 cross join cteNums num2 go Create table #LookupTable ( Id integer not null, SubID integer null ) go insert into #LookupTable Select top(100) id,subid from #SourceTable where subid is not null order by newid() go insert into #LookupTable Select top(3) id,subid from #SourceTable where subid is null order by newid() If that has run correctly, you will have 1 million rows in #SourceTable and 103 rows in #LookupTable.  We now want to join one to the other. First attempt – Lets just join select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and #LookupTable.SubID = #SourceTable.SubID OK, that’s a fail.  We had 100 rows back,  we didn’t correctly account for the 3 rows that have null values.  Remember NULL <> NULL and the join clause specifies SUBID=SUBID, which for those rows is not true. Second attempt – Lets deal with those pesky NULLS select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and isnull(#LookupTable.SubID,0) = isnull(#SourceTable.SubID,0) OK, that’s the right result, well done and 99.9% of the time that is where its left. It is a relatively trivial CPU overhead to wrap ISNULL around both columns and compare that result, so no problems.  But, although that’s true, this a relational database we are using here, not a procedural language.  SQL is a declarative language, we are making a request to the engine to get the results we want.  How we ask for them can make a ton of difference. Lets look at the plan for our second attempt, specifically the clustered index seek on the #SourceTable   There are 2 predicates. The ‘seek predicate’ and ‘predicate’.  The ‘seek predicate’ describes how SQLServer has been able to use an Index.  Here, it has been able to navigate the index to resolve where ID=ID.  So far so good, but what about the ‘predicate’ (aka residual probe) ? This is a row-by-row operation.  For each row found in the index matching the Seek Predicate, the leaf level nodes have been scanned and tested using this logical condition.  In this example [Expr1007] is the result of the IsNull operation on #LookupTable and that is tested for equality with the IsNull operation on #SourceTable.  This residual probe is quite a high overhead, if we can express our statement slightly differently to take full advantage of the index and make the test part of the ‘Seek Predicate’. Third attempt – X is null and Y is null So, lets state the query in a slightly manner: select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and ( #LookupTable.SubID = #SourceTable.SubID or (#LookupTable.SubID is null and #SourceTable.SubId is null) ) So its slightly wordier and may not be as clear in its intent to the human reader, that is what comments are for, but the key point is that it is now clearer to the query optimizer what our intention is. Let look at the plan for that query, again specifically the index seek operation on #SourceTable No ‘predicate’, just a ‘Seek Predicate’ against the index to resolve both ID and SubID.  A subtle difference that can be easily overlooked.  But has it made a difference to the performance ? Well, yes , a perhaps surprisingly high one. Clever query optimizer well done. If you are using a scalar function on a column, you a pretty much guaranteeing that a residual probe will be used.  By re-wording the query you may well be able to avoid this and use the index completely to resolve lookups. In-terms of performance and scalability your system will be in a much better position if you can.

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • Local LINQtoSQL Database For Your Windows Phone 7 Application

    - by Tim Murphy
    There aren’t many applications that are of value without having some for of data store.  In Windows Phone development we have a few options.  You can store text directly to isolated storage.  You can also use a number of third party libraries to create or mimic databases in isolated storage.  With Mango we gained the ability to have a native .NET database approach which uses LINQ to SQL.  In this article I will try to bring together the components needed to implement this last type of data store and fill in some of the blanks that I think other articles have left out. Defining A Database The first things you are going to need to do is define classes that represent your tables and a data context class that is used as the overall database definition.  The table class consists of column definitions as you would expect.  They can have relationships and constraints as with any relational DBMS.  Below is an example of a table definition. First you will need to add some assembly references to the code file. using System.ComponentModel;using System.Data.Linq;using System.Data.Linq.Mapping; You can then add the table class and its associated columns.  It needs to implement INotifyPropertyChanged and INotifyPropertyChanging.  Each level of the class needs to be decorated with the attribute appropriate for that part of the definition.  Where the class represents the table the properties represent the columns.  In this example you will see that the column is marked as a primary key and not nullable with a an auto generated value. You will also notice that the in the column property’s set method It uses the NotifyPropertyChanging and NotifyPropertyChanged methods in order to make sure that the proper events are fired. [Table]public class MyTable: INotifyPropertyChanged, INotifyPropertyChanging{ public event PropertyChangedEventHandler PropertyChanged; private void NotifyPropertyChanged(string propertyName) { if(PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } public event PropertyChangingEventHandler PropertyChanging; private void NotifyPropertyChanging(string propertyName) { if(PropertyChanging != null) { PropertyChanging(this, new PropertyChangingEventArgs(propertyName)); } } private int _TableKey; [Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)] public int TableKey { get { return _TableKey; } set { NotifyPropertyChanging("TableKey"); _TableKey = value; NotifyPropertyChanged("TableKey"); } } The last part of the database definition that needs to be created is the data context.  This is a simple class that takes an isolated storage location connection string its constructor and then instantiates tables as public properties. public class MyDataContext: DataContext{ public MyDataContext(string connectionString): base(connectionString) { MyRecords = this.GetTable<MyTable>(); } public Table<MyTable> MyRecords;} Creating A New Database Instance Now that we have a database definition it is time to create an instance of the data context within our Windows Phone app.  When your app fires up it should check if the database already exists and create an instance if it does not.  I would suggest that this be part of the constructor of your ViewModel. db = new MyDataContext(connectionString);if(!db.DatabaseExists()){ db.CreateDatabase();} The next thing you have to know is how the connection string for isolated storage should be constructed.  The main sticking point I have found is that the database cannot be created unless the file mode is read/write.  You may have different connection strings but the initial one needs to be similar to the following. string connString = "Data Source = 'isostore:/MyApp.sdf'; File Mode = read write"; Using you database Now that you have done all the up front work it is time to put the database to use.  To make your life a little easier and keep proper separation between your view and your viewmodel you should add a couple of methods to the viewmodel.  These will do the CRUD work of your application.  What you will notice is that the SubmitChanges method is the secret sauce in all of the methods that change data. private myDataContext myDb;private ObservableCollection<MyTable> _viewRecords;public ObservableCollection<MyTable> ViewRecords{ get { return _viewRecords; } set { _viewRecords = value; NotifyPropertyChanged("ViewRecords"); }}public void LoadMedstarDbData(){ var tempItems = from MyTable myRecord in myDb.LocalScans select myRecord; ViewRecords = new ObservableCollection<MyTable>(tempItems);}public void SaveChangesToDb(){ myDb.SubmitChanges();}public void AddMyTableItem(MyTable newScan){ myDb.LocalScans.InsertOnSubmit(newScan); myDb.SubmitChanges();}public void DeleteMyTableItem(MyTable newScan){ myDb.LocalScans.DeleteOnSubmit(newScan); myDb.SubmitChanges();} Updating existing database What happens when you need to change the structure of your database?  Unfortunately you have to add code to your application that checks the version of the database which over time will create some pollution in your codes base.  On the other hand it does give you control of the update.  In this example you will see the DatabaseSchemaUpdater in action.  Assuming we added a “Notes” field to the MyTable structure, the following code will check if the database is the latest version and add the field if it isn’t. if(!myDb.DatabaseExists()){ myDb.CreateDatabase();}else{ DatabaseSchemaUpdater dbUdater = myDb.CreateDatabaseSchemaUpdater(); if(dbUdater.DatabaseSchemaVersion < 2) { dbUdater.AddColumn<MyTable>("Notes"); dbUdater.DatabaseSchemaVersion = 2; dbUdater.Execute(); }} Summary This approach does take a fairly large amount of work, but I think the end product is robust and very native for .NET developers.  It turns out to be worth the investment. del.icio.us Tags: Windows Phone,Windows Phone 7,LINQ to SQL,LINQ,Database,Isolated Storage

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  • Using MVC2 to update an Entity Framework v4 object with foreign keys fails

    - by jbjon
    With the following simple relational database structure: An Order has one or more OrderItems, and each OrderItem has one OrderItemStatus. Entity Framework v4 is used to communicate with the database and entities have been generated from this schema. The Entities connection happens to be called EnumTestEntities in the example. The trimmed down version of the Order Repository class looks like this: public class OrderRepository { private EnumTestEntities entities = new EnumTestEntities(); // Query Methods public Order Get(int id) { return entities.Orders.SingleOrDefault(d => d.OrderID == id); } // Persistence public void Save() { entities.SaveChanges(); } } An MVC2 app uses Entity Framework models to drive the views. I'm using the EditorFor feature of MVC2 to drive the Edit view. When it comes to POSTing back any changes to the model, the following code is called: [HttpPost] public ActionResult Edit(int id, FormCollection formValues) { // Get the current Order out of the database by ID Order order = orderRepository.Get(id); var orderItems = order.OrderItems; try { // Update the Order from the values posted from the View UpdateModel(order, ""); // Without the ValueProvider suffix it does not attempt to update the order items UpdateModel(order.OrderItems, "OrderItems.OrderItems"); // All the Save() does is call SaveChanges() on the database context orderRepository.Save(); return RedirectToAction("Details", new { id = order.OrderID }); } catch (Exception e) { return View(order); // Inserted while debugging } } The second call to UpdateModel has a ValueProvider suffix which matches the auto-generated HTML input name prefixes that MVC2 has generated for the foreign key collection of OrderItems within the View. The call to SaveChanges() on the database context after updating the OrderItems collection of an Order using UpdateModel generates the following exception: "The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted." When debugging through this code, I can still see that the EntityKeys are not null and seem to be the same value as they should be. This still happens when you are not changing any of the extracted Order details from the database. Also the entity connection to the database doesn't change between the act of Getting and the SaveChanges so it doesn't appear to be a Context issue either. Any ideas what might be causing this problem? I know EF4 has done work on foreign key properties but can anyone shed any light on how to use EF4 and MVC2 to make things easy to update; rather than having to populate each property manually. I had hoped the simplicity of EditorFor and DisplayFor would also extend to Controllers updating data. Thanks

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  • SQL Server to PostgreSQL - Migration and design concerns

    - by youwhut
    Currently migrating from SQL Server to PostgreSQL and attempting to improve a couple of key areas on the way: I have an Articles table: CREATE TABLE [dbo].[Articles]( [server_ref] [int] NOT NULL, [article_ref] [int] NOT NULL, [article_title] [varchar](400) NOT NULL, [category_ref] [int] NOT NULL, [size] [bigint] NOT NULL ) Data (comma delimited text files) is dumped on the import server by ~500 (out of ~1000) servers on a daily basis. Importing: Indexes are disabled on the Articles table. For each dumped text file Data is BULK copied to a temporary table. Temporary table is updated. Old data for the server is dropped from the Articles table. Temporary table data is copied to Articles table. Temporary table dropped. Once this process is complete for all servers the indexes are built and the new database is copied to a web server. I am reasonably happy with this process but there is always room for improvement as I strive for a real-time (haha!) system. Is what I am doing correct? The Articles table contains ~500 million records and is expected to grow. Searching across this table is okay but could be better. i.e. SELECT * FROM Articles WHERE server_ref=33 AND article_title LIKE '%criteria%' has been satisfactory but I want to improve the speed of searching. Obviously the "LIKE" is my problem here. Suggestions? SELECT * FROM Articles WHERE article_title LIKE '%criteria%' is horrendous. Partitioning is a feature of SQL Server Enterprise but $$$ which is one of the many exciting prospects of PostgreSQL. What performance hit will be incurred for the import process (drop data, insert data) and building indexes? Will the database grow by a huge amount? The database currently stands at 200 GB and will grow. Copying this across the network is not ideal but it works. I am putting thought into changing the hardware structure of the system. The thought process of having an import server and a web server is so that the import server can do the dirty work (WITHOUT indexes) while the web server (WITH indexes) can present reports. Maybe reducing the system down to one server would work to skip the copying across the network stage. This one server would have two versions of the database: one with the indexes for delivering reports and the other without for importing new data. The databases would swap daily. Thoughts? This is a fantastic system, and believe it or not there is some method to my madness by giving it a big shake up. UPDATE: I am not looking for help with relational databases, but hoping to bounce ideas around with data warehouse experts.

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  • jquery data selector

    - by Tauren
    I need to select elements based on values stored in an element's .data() object. At a minimum, I'd like to select top-level data properties using selectors, perhaps like this: $('a').data("category","music"); $('a:data(category=music)'); Or perhaps the selector would be in regular attribute selector format: $('a[category=music]'); Or in attribute format, but with a specifier to indicate it is in .data(): $('a[:category=music]'); I've found James Padolsey's implementation to look simple, yet good. The selector formats above mirror methods shown on that page. There is also this Sizzle patch. For some reason, I recall reading a while back that jQuery 1.4 would include support for selectors on values in the jquery .data() object. However, now that I'm looking for it, I can't find it. Maybe it was just a feature request that I saw. Is there support for this and I'm just not seeing it? Ideally, I'd like to support sub-properties in data() using dot notation. Like this: $('a').data("user",{name: {first:"Tom",last:"Smith"},username: "tomsmith"}); $('a[:user.name.first=Tom]'); I also would like to support multiple data selectors, where only elements with ALL specified data selectors are found. The regular jquery multiple selector does an OR operation. For instance, $('a.big, a.small') selects a tags with either class big or small). I'm looking for an AND, perhaps like this: $('a').data("artist",{id: 3281, name: "Madonna"}); $('a').data("category","music"); $('a[:category=music && :artist.name=Madonna]'); Lastly, it would be great if comparison operators and regex features were available on data selectors. So $(a[:artist.id>5000]) would be possible. I realize I could probably do much of this using filter(), but it would be nice to have a simple selector format. What solutions are available to do this? Is Jame's Padolsey's the best solution at this time? My concern is primarily in regards to performance, but also in the extra features like sub-property dot-notation and multiple data selectors. Are there other implementations that support these things or are better in some way?

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  • how to store xml structure in a persistence layer?

    - by fayer
    i wonder how i could store a xml structure in a persistence layer. cause the relational data looks like: <entity id="1000070"> <name>apple</name> <entities> <entity id="7002870"> <name>mac</name> <entities> <entity id="7002907"> <name>leopard</name> <entities> <entity id="7024080"> <name>safari</name> </entity> <entity id="7024701"> <name>finder</name> </entity> </entities> </entity> </entities> </entity> <entity id="7024080"> <name>iphone</name> <entities> <entity id="7024080"> <name>3g</name> </entity> <entity id="7024701"> <name>3gs</name> </entity> </entities> </entity> <entity id="7024080"> <name>ipad</name> </entity> </entities> </entity> as you can see, it has no static structure but a dynamical one. mac got 2 descendant levels while iphone got 1 and ipad got 0. i wonder how i could store this data the best way? what are my options. cause it seems impossible to store it in a mysql database due to this dynamical structure. is the only way to store it as a xml file then? is the speed of getting information (xpath/xquery/simplexml) from a xml file worse or greater than from mysql? what are the pros and cons? do i have other options? is storing information in xml files, suited for a lot of users accessing it at the same time? would be great with feedbacks!! thanks!

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  • Fixed point math in c#?

    - by x4000
    Hi there, I was wondering if anyone here knows of any good resources for fixed point math in c#? I've seen things like this (http://2ddev.72dpiarmy.com/viewtopic.php?id=156) and this (http://stackoverflow.com/questions/79677/whats-the-best-way-to-do-fixed-point-math), and a number of discussions about whether decimal is really fixed point or actually floating point (update: responders have confirmed that it's definitely floating point), but I haven't seen a solid C# library for things like calculating cosine and sine. My needs are simple -- I need the basic operators, plus cosine, sine, arctan2, PI... I think that's about it. Maybe sqrt. I'm programming a 2D RTS game, which I have largely working, but the unit movement when using floating-point math (doubles) has very small inaccuracies over time (10-30 minutes) across multiple machines, leading to desyncs. This is presently only between a 32 bit OS and a 64 bit OS, all the 32 bit machines seem to stay in sync without issue, which is what makes me think this is a floating point issue. I was aware from this as a possible issue from the outset, and so have limited my use of non-integer position math as much as possible, but for smooth diagonal movement at varying speeds I'm calculating the angle between points in radians, then getting the x and y components of movement with sin and cos. That's the main issue. I'm also doing some calculations for line segment intersections, line-circle intersections, circle-rect intersections, etc, that also probably need to move from floating-point to fixed-point to avoid cross-machine issues. If there's something open source in Java or VB or another comparable language, I could probably convert the code for my uses. The main priority for me is accuracy, although I'd like as little speed loss over present performance as possible. This whole fixed point math thing is very new to me, and I'm surprised by how little practical information on it there is on google -- most stuff seems to be either theory or dense C++ header files. Anything you could do to point me in the right direction is much appreciated; if I can get this working, I plan to open-source the math functions I put together so that there will be a resource for other C# programmers out there. UPDATE: I could definitely make a cosine/sine lookup table work for my purposes, but I don't think that would work for arctan2, since I'd need to generate a table with about 64,000x64,000 entries (yikes). If you know any programmatic explanations of efficient ways to calculate things like arctan2, that would be awesome. My math background is all right, but the advanced formulas and traditional math notation are very difficult for me to translate into code.

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  • Code Golf: Evaluating Mathematical Expressions

    - by Noldorin
    Challenge Here is the challenge (of my own invention, though I wouldn't be surprised if it has previously appeared elsewhere on the web). Write a function that takes a single argument that is a string representation of a simple mathematical expression and evaluates it as a floating point value. A "simple expression" may include any of the following: positive or negative decimal numbers, +, -, *, /, (, ). Expressions use (normal) infix notation. Operators should be evaluated in the order they appear, i.e. not as in BODMAS, though brackets should be correctly observed, of course. The function should return the correct result for any possible expression of this form. However, the function does not have to handle malformed expressions (i.e. ones with bad syntax). Examples of expressions: 1 + 3 / -8 = -0.5 (No BODMAS) 2*3*4*5+99 = 219 4 * (9 - 4) / (2 * 6 - 2) + 8 = 10 1 + ((123 * 3 - 69) / 100) = 4 2.45/8.5*9.27+(5*0.0023) = 2.68... Rules I anticipate some form of "cheating"/craftiness here, so please let me forewarn against it! By cheating, I refer to the use of the eval or equivalent function in dynamic languages such as JavaScript or PHP, or equally compiling and executing code on the fly. (I think my specification of "no BODMAS" has pretty much guaranteed this however.) Apart from that, there are no restrictions. I anticipate a few Regex solutions here, but it would be nice to see more than just that. Now, I'm mainly interested in a C#/.NET solution here, but any other language would be perfectly acceptable too (in particular, F# and Python for the functional/mixed approaches). I haven't yet decided whether I'm going to accept the shortest or most ingenious solution (at least for the language) as the answer, but I would welcome any form of solution in any language, except what I've just prohibited above! My Solution I've now posted my C# solution here (403 chars). Update: My new solution has beaten the old one significantly at 294 chars, with the help of a bit of lovely regex! I suspected that this will get easily beaten by some of the languages out there with lighter syntax (particularly the funcional/dynamic ones), and have been proved right, but I'd be curious if someone could beat this in C# still. Update I've seen some very crafty solutions already. Thanks to everyone who has posted one. Although I haven't tested any of them yet, I'm going to trust people and assume they at least work with all of the given examples. Just for the note, re-entrancy (i.e. thread-safety) is not a requirement for the function, though it is a bonus. Format Please post all answers in the following format for the purpose of easy comparison: Language Number of characters: ??? Fully obfuscated function: (code here) Clear/semi-obfuscated function: (code here) Any notes on the algorithm/clever shortcuts it takes.

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  • Yii - Custom GridView with Multiple Tables

    - by savinger
    So, I've extended GridView to include an Advanced Search feature tailored to the needs of my organization. Filter - lets you show/hide columns in the table, and you can also reorder columns by dragging the little drag icon to the left of each item. Sort - Allows for the selection of multiple columns, specify Ascending or Descending. Search - Select your column and insert search parameters. Operators tailored to data type of selected column. Version 1 works, albeit slowly. Basically, I had my hands in the inner workings of CGridView, where I snatch the results from the DataProvider and do the searching and sorting in PHP before rendering the table contents. Now writing Version 2, where I aim to focus on clever CDbCriteria creation, allowing MySQL to do the heavy lifting so it will run quicker. The implementation is trivial when dealing with a single database table. The difficulty arises when I'm dealing with 2 or more tables... For example, if the user intends to search on a field that is a STAT relation, I need that relation to be present in my query. Here's the question. How do I assure that Yii includes all with relations in my query so that I include comparisons? I've included all my relations with my criteria in the model's search function and I've tried CDbCriteria's together ... public function search() { $criteria=new CDbCriteria; $criteria->compare('id', $this->id); $criteria->compare( ... ... $criteria->with = array('relation1','relation2','relation3'); $criteria->together = true; return new CActiveDataProvider( get_class($this), array( 'criteria'=>$criteria, 'pagination' => array('pageSize' => 50) ));} But I still get errors like this... CDbCommand failed to execute the SQL statement: SQLSTATE[42S22]: Column not found: 1054 Unknown column 't.relation3' in 'where clause'. The SQL statement executed was: SELECT COUNT(DISTINCT `t`.`id`) FROM `table` `t` LEFT OUTER JOIN `relation_table` `relation0` ON (`t`.`id`=`relation0`.`id`) LEFT OUTER JOIN `relation_table` `relation1` ON (`t`.`id`=`relation1`.`id`) WHERE (`t`.`relation3` < 1234567890) Where relation0 and relation1 are BELONGS_TO relations, but any STAT relations are missing. Furthermore, why is the query a SELECT COUNT(DISTINCT 't'.'id') ?

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