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  • SQL SERVER – Simple Example to Configure Resource Governor – Introduction to Resource Governor

    - by pinaldave
    Let us jump right away with question and answer mode. What is resource governor? Resource Governor is a feature which can manage SQL Server Workload and System Resource Consumption. We can limit the amount of CPU and memory consumption by limiting /governing /throttling on the SQL Server. Why is resource governor required? If there are different workloads running on SQL Server and each of the workload needs different resources or when workloads are competing for resources with each other and affecting the performance of the whole server resource governor is a very important task. What will be the real world example of need of resource governor? Here are two simple scenarios where the resource governor can be very useful. Scenario 1: A server which is running OLTP workload and various resource intensive reports on the same server. The ideal situation is where there are two servers which are data synced with each other and one server runs OLTP transactions and the second server runs all the resource intensive reports. However, not everybody has the luxury to set up this kind of environment. In case of the situation where reports and OLTP transactions are running on the same server, limiting the resources to the reporting workload it can be ensured that OTLP’s critical transaction is not throttled. Scenario 2: There are two DBAs in one organization. One DBA A runs critical queries for business and another DBA B is doing maintenance of the database. At any point in time the DBA A’s work should not be affected but at the same time DBA B should be allowed to work as well. The ideal situation is that when DBA B starts working he get some resources but he can’t get more than defined resources. Does SQL Server have any default resource governor component? Yes, SQL Server have two by default created resource governor component. 1) Internal –This is used by database engine exclusives and user have no control. 2) Default – This is used by all the workloads which are not assigned to any other group. What are the major components of the resource governor? Resource Pools Workload Groups Classification In simple words here is what the process of resource governor is. Create resource pool Create a workload group Create classification function based on the criteria specified Enable Resource Governor with classification function Let me further explain you the same with graphical image. Is it possible to configure resource governor with T-SQL? Yes, here is the code for it with explanation in between. Step 0: Here we are assuming that there are separate login accounts for Reporting server and OLTP server. /*----------------------------------------------- Step 0: (Optional and for Demo Purpose) Create Two User Logins 1) ReportUser, 2) PrimaryUser Use ReportUser login for Reports workload Use PrimaryUser login for OLTP workload -----------------------------------------------*/ Step 1: Creating Resource Pool We are creating two resource pools. 1) Report Server and 2) Primary OLTP Server. We are giving only a few resources to the Report Server Pool as described in the scenario 1 the other server is mission critical and not the report server. ----------------------------------------------- -- Step 1: Create Resource Pool ----------------------------------------------- -- Creating Resource Pool for Report Server CREATE RESOURCE POOL ReportServerPool WITH ( MIN_CPU_PERCENT=0, MAX_CPU_PERCENT=30, MIN_MEMORY_PERCENT=0, MAX_MEMORY_PERCENT=30) GO -- Creating Resource Pool for OLTP Primary Server CREATE RESOURCE POOL PrimaryServerPool WITH ( MIN_CPU_PERCENT=50, MAX_CPU_PERCENT=100, MIN_MEMORY_PERCENT=50, MAX_MEMORY_PERCENT=100) GO Step 2: Creating Workload Group We are creating two workloads each mapping to each of the resource pool which we have just created. ----------------------------------------------- -- Step 2: Create Workload Group ----------------------------------------------- -- Creating Workload Group for Report Server CREATE WORKLOAD GROUP ReportServerGroup USING ReportServerPool ; GO -- Creating Workload Group for OLTP Primary Server CREATE WORKLOAD GROUP PrimaryServerGroup USING PrimaryServerPool ; GO Step 3: Creating user defiled function which routes the workload to the appropriate workload group. In this example we are checking SUSER_NAME() and making the decision of Workgroup selection. We can use other functions such as HOST_NAME(), APP_NAME(), IS_MEMBER() etc. ----------------------------------------------- -- Step 3: Create UDF to Route Workload Group ----------------------------------------------- CREATE FUNCTION dbo.UDFClassifier() RETURNS SYSNAME WITH SCHEMABINDING AS BEGIN DECLARE @WorkloadGroup AS SYSNAME IF(SUSER_NAME() = 'ReportUser') SET @WorkloadGroup = 'ReportServerGroup' ELSE IF (SUSER_NAME() = 'PrimaryServerPool') SET @WorkloadGroup = 'PrimaryServerGroup' ELSE SET @WorkloadGroup = 'default' RETURN @WorkloadGroup END GO Step 4: In this final step we enable the resource governor with the classifier function created in earlier step 3. ----------------------------------------------- -- Step 4: Enable Resource Governer -- with UDFClassifier ----------------------------------------------- ALTER RESOURCE GOVERNOR WITH (CLASSIFIER_FUNCTION=dbo.UDFClassifier); GO ALTER RESOURCE GOVERNOR RECONFIGURE GO Step 5: If you are following this demo and want to clean up your example, you should run following script. Running them will disable your resource governor as well delete all the objects created so far. ----------------------------------------------- -- Step 5: Clean Up -- Run only if you want to clean up everything ----------------------------------------------- ALTER RESOURCE GOVERNOR WITH (CLASSIFIER_FUNCTION = NULL) GO ALTER RESOURCE GOVERNOR DISABLE GO DROP FUNCTION dbo.UDFClassifier GO DROP WORKLOAD GROUP ReportServerGroup GO DROP WORKLOAD GROUP PrimaryServerGroup GO DROP RESOURCE POOL ReportServerPool GO DROP RESOURCE POOL PrimaryServerPool GO ALTER RESOURCE GOVERNOR RECONFIGURE GO I hope this introductory example give enough light on the subject of Resource Governor. In future posts we will take this same example and learn a few more details. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Resource Governor

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  • SQLAuthority News – Storing Data and Files in Cloud – Dropbox – Personal Technology Tip

    - by pinaldave
    I thought long and hard about doing a Personal Technology Tips series for this blog.  I have so many tips I’d like to share.  I am on my computer almost all day, every day, so I have a treasure trove of interesting tidbits I like to share if given the chance.  The only thing holding me back – which tip to share first?  The first tip obviously has the weight of seeming like the most important.  But this would mean choosing amongst my favorite tricks and shortcuts.  This is a hard task. Source: Dropbox.com My Dropbox I have finally decided, though, and have determined that the first Personal Technology Tip may not be the most secret or even trickier to master – in fact, it is probably the easiest.  My today’s Personal Technology Tip is Dropbox. I hope that all of you are nodding along in recognition right now.  If you do not use Dropbox, or have not even heard of it before, get on the internet and find their site.  You won’t be disappointed.  A quick recap for those in the dark: Dropbox is an online storage site with a lot of additional syncing and cloud-computing capabilities.  Now that we’ve covered the basics, let’s explore some of my favorite options in Dropbox. Collaborate with All The first thing I love about Dropbox is the ability it gives you to collaborate with others.  You can share files easily with other Dropbox users, and they can alter them, share them with you, all while keeping track of different versions in on easy place.  I’d like to see anyone try to accomplish that key idea – “easily” – using e-mail versions and multiple computers.  It’s even difficult to accomplish using a shared network. Afraid that this kind of ease looks too good to be true?  Afraid that maybe there isn’t enough storage space, or the user interface is confusing?  Think again.  There is plenty of space – you can get 2 GB with just a free account, and upgrades are inexpensive and go up to 100 GB of storage.  And the user interface is so easy that anyone can learn to use it. What I use Dropbox for I love Dropbox because I give a lot of presentations and often they are far from home.  I can keep my presentations on Dropbox and have easy access to them anywhere, without needing to have my whole computer with me.  This is just one small way that you can use Dropbox. You can sync your entire hard drive, or hard drives if you have multiple computers (home, work, office, shared), and you can set Dropbox to automatically sync files on a certain timeline, or whenever Dropbox notices that they’ve been changed. Why I love Dropbox Dropbox has plenty of storage, but 2 GB still has a hard time competing with the average desktop’s storage space.  So what if you want to sync most of your files, but only the ones you use the most and share between work and home, and not all your files (especially large files like pictures and videos)?  You can use selective sync to choose which files to sync. Above all, my favorite feature is LanSync.  Dropbox will search your Local Area Network (LAN) for new files and sync them to Dropbox, as well as downloading the new version to all the shared files across the network.  That means that if move around on different computers at work or at home, you will have the same version of the file every time.  Or, other users on the LAN will have access to the new version, which makes collaboration extremely easy. Ref: rzfeeser.com Dropbox has so many other features that I feel like I could create a Personal Technology Tips series devoted entirely to Dropbox.  I’m going to create a bullet list here to make things shorter, but I strongly encourage you to look further into these into options if it sounds like something you would use. Theft Recover Home Security File Hosting and Sharing Portable Dropbox Sync your iCal calendar Password Storage What is your favorite tool and why? I could go on and on, but I will end here.  In summary – I strongly encourage everyone to investigate Dropbox to see if it’s something they would find useful.  If you use Dropbox and know of a great feature I failed to mention, please share it with me, I’d love to hear how everyone uses this program. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology Tagged: Personal Technology

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  • SQL SERVER – Auditing and Profiling Database Made Easy with SQL Audit and Comply

    - by Pinal Dave
    Do you like auditing your database, or can you think of about a million other things you’d rather do?  Unfortunately, auditing is incredibly important.  As with tax audits, it is important to audit databases to ensure they are following all the rules, but they are also important for troubleshooting and security. There are several ways to audit SQL Server.  There is manual auditing, which is going through your database “by hand,” and obviously takes a long time and is quite inefficient.  SQL Server also provides programs to help you audit your systems.  Different administrators will have different opinions about best practices and which tools to use, and each one will be perfected for certain systems and certain users. Today, though, I would like to talk about Apex SQL Audit.  It is an auditing tool that acts like “track changes” in a word processing document.  It will log what has changed on the database, who made the changes, and what effects these changes have had (i.e. what objects were affected down the line).  All this information is logged, and can be easily viewed or printed for easy access. One of the best features of Apex is that it is so customizable (and easy to use!).  First, start Apex.  Then you can connect to the database you would like to monitor. Once you select your database, you can select which table you want to audit. You can customize right down to the field you’d like to audit, and then select which types of actions you’d like tracked – insert, delete, or update.  Repeat these steps for every database you want monitored. To create the logs, choose “Create triggers” in the menu.  The script written here will be what logs each insert, delete, and update function.  Press F5 to execute.  All this tracking information will be stored in AUDIT_LOG_DATA and AUDIT_LOG_TRANSACTIONS tables.  View these tables using ApexSQL Audit reports. These transaction logs can be extremely detailed – especially on very busy servers, where every move it traced.  Reading them can be overwhelming, to say the least.  Apex has tried to make things easier for the average DBA, though. You can read these tracking logs in Apex, and it will display data and objects that affect your server – even things that were happening on your server before you installed Apex! To read these logs, open Apex, and connect to that database you want to audit. Go to the Transaction Logs tab, and add the logs you want to read. To narrow down what results you want to see, you can use the Filter tab to choose time, operation type, name, users, and more. Click Open, and you can see the results in a grid (as shown below).  You can export these results to CSV, HTML, XML or SQL files and save on the hard disk. One of the advantages is that since there are no triggers here, there are no other processes that will affect SQL Server performance.  Using this method is also how to view history from your database that occurred before Apex was installed.  This type of tracking does require storage space for the data sources, as the database must be fully running, and the transaction logs must exist (things not stored in the transactions logs will not be recoverable). Apex can also replace SQL Server Profiler and SQL Server Traces – which are much more complex and error-prone – with its ApexSQL Comply.  It can do fault tolerant auditing, centralized reporting, and “who saw what” information in an easy-to-use interface.  The tracking settings can be altered by the user, or the default options will provide solutions to the most common auditing problems. To get started: open ApexSQL Comply, and selected Database Filter Settings to choose which database you’d like to audit.  You can select which tracking you’re like in Operation Types – DML, DDL, queries executed, execute statements, and more.  To get started, click Start Auditing. After this, every action will be stored in the central repository database (ApexSQLCrd).  You can view the audit and create a report (or view the standard default report) using a wizard. You can see how easy it is to use ApexSQL Comply.  You can easily set audits, including the type and time, and create customized reports.  Remote users can easily access the reports through the user interface (available online, as well), and security concerns are all taken care of by the program.  Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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  • SQL SERVER – Simple Example of Incremental Statistics – Performance improvements in SQL Server 2014 – Part 2

    - by Pinal Dave
    This is the second part of the series Incremental Statistics. Here is the index of the complete series. What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1 Simple Example of Incremental Statistics – Performance improvements in SQL Server 2014 – Part 2 DMV to Identify Incremental Statistics – Performance improvements in SQL Server 2014 – Part 3 In part 1 we have understood what is incremental statistics and now in this second part we will see a simple example of incremental statistics. This blog post is heavily inspired from my friend Balmukund’s must read blog post. If you have partitioned table and lots of data, this feature can be specifically very useful. Prerequisite Here are two things you must know before you start with the demonstrations. AdventureWorks – For the demonstration purpose I have installed AdventureWorks 2012 as an AdventureWorks 2014 in this demonstration. Partitions – You should know how partition works with databases. Setup Script Here is the setup script for creating Partition Function, Scheme, and the Table. We will populate the table based on the SalesOrderDetails table from AdventureWorks. -- Use Database USE AdventureWorks2014 GO -- Create Partition Function CREATE PARTITION FUNCTION IncrStatFn (INT) AS RANGE LEFT FOR VALUES (44000, 54000, 64000, 74000) GO -- Create Partition Scheme CREATE PARTITION SCHEME IncrStatSch AS PARTITION [IncrStatFn] TO ([PRIMARY], [PRIMARY], [PRIMARY], [PRIMARY], [PRIMARY]) GO -- Create Table Incremental_Statistics CREATE TABLE [IncrStatTab]( [SalesOrderID] [int] NOT NULL, [SalesOrderDetailID] [int] NOT NULL, [CarrierTrackingNumber] [nvarchar](25) NULL, [OrderQty] [smallint] NOT NULL, [ProductID] [int] NOT NULL, [SpecialOfferID] [int] NOT NULL, [UnitPrice] [money] NOT NULL, [UnitPriceDiscount] [money] NOT NULL, [ModifiedDate] [datetime] NOT NULL) ON IncrStatSch(SalesOrderID) GO -- Populate Table INSERT INTO [IncrStatTab]([SalesOrderID], [SalesOrderDetailID], [CarrierTrackingNumber], [OrderQty], [ProductID], [SpecialOfferID], [UnitPrice],   [UnitPriceDiscount], [ModifiedDate]) SELECT     [SalesOrderID], [SalesOrderDetailID], [CarrierTrackingNumber], [OrderQty], [ProductID], [SpecialOfferID], [UnitPrice],   [UnitPriceDiscount], [ModifiedDate] FROM       [Sales].[SalesOrderDetail] WHERE      SalesOrderID < 54000 GO Check Details Now we will check details in the partition table IncrStatSch. -- Check the partition SELECT * FROM sys.partitions WHERE OBJECT_ID = OBJECT_ID('IncrStatTab') GO You will notice that only a few of the partition are filled up with data and remaining all the partitions are empty. Now we will create statistics on the Table on the column SalesOrderID. However, here we will keep adding one more keyword which is INCREMENTAL = ON. Please note this is the new keyword and feature added in SQL Server 2014. It did not exist in earlier versions. -- Create Statistics CREATE STATISTICS IncrStat ON [IncrStatTab] (SalesOrderID) WITH FULLSCAN, INCREMENTAL = ON GO Now we have successfully created statistics let us check the statistical histogram of the table. Now let us once again populate the table with more data. This time the data are entered into a different partition than earlier populated partition. -- Populate Table INSERT INTO [IncrStatTab]([SalesOrderID], [SalesOrderDetailID], [CarrierTrackingNumber], [OrderQty], [ProductID], [SpecialOfferID], [UnitPrice],   [UnitPriceDiscount], [ModifiedDate]) SELECT     [SalesOrderID], [SalesOrderDetailID], [CarrierTrackingNumber], [OrderQty], [ProductID], [SpecialOfferID], [UnitPrice],   [UnitPriceDiscount], [ModifiedDate] FROM       [Sales].[SalesOrderDetail] WHERE      SalesOrderID > 54000 GO Let us check the status of the partition once again with following script. -- Check the partition SELECT * FROM sys.partitions WHERE OBJECT_ID = OBJECT_ID('IncrStatTab') GO Statistics Update Now here has the new feature come into action. Previously, if we have to update the statistics, we will have to FULLSCAN the entire table irrespective of which partition got the data. However, in SQL Server 2014 we can just specify which partition we want to update in terms of Statistics. Here is the script for the same. -- Update Statistics Manually UPDATE STATISTICS IncrStatTab (IncrStat) WITH RESAMPLE ON PARTITIONS(3, 4) GO Now let us check the statistics once again. -- Show Statistics DBCC SHOW_STATISTICS('IncrStatTab', IncrStat) WITH HISTOGRAM GO Upon examining statistics histogram, you will notice that now the distribution has changed and there is way more rows in the histogram. Summary The new feature of Incremental Statistics is indeed a boon for the scenario where there are partitions and statistics needs to be updated frequently on the partitions. In earlier version to update statistics one has to do FULLSCAN on the entire table which was wasting too many resources. With the new feature in SQL Server 2014, now only those partitions which are significantly changed can be specified in the script to update statistics. Cleanup You can clean up the database by executing following scripts. -- Clean up DROP TABLE [IncrStatTab] DROP PARTITION SCHEME [IncrStatSch] DROP PARTITION FUNCTION [IncrStatFn] GO Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SQL Statistics, Statistics

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  • Big Data – Evolution of Big Data – Day 3 of 21

    - by Pinal Dave
    In yesterday’s blog post we answered what is the Big Data. Today we will understand why and how the evolution of Big Data has happened. Though the answer is very simple, I would like to tell it in the form of a history lesson. Data in Flat File In earlier days data was stored in the flat file and there was no structure in the flat file.  If any data has to be retrieved from the flat file it was a project by itself. There was no possibility of retrieving the data efficiently and data integrity has been just a term discussed without any modeling or structure around. Database residing in the flat file had more issues than we would like to discuss in today’s world. It was more like a nightmare when there was any data processing involved in the application. Though, applications developed at that time were also not that advanced the need of the data was always there and there was always need of proper data management. Edgar F Codd and 12 Rules Edgar Frank Codd was a British computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases. He presented 12 rules for the Relational Database and suddenly the chaotic world of the database seems to see discipline in the rules. Relational Database was a promising land for all the unstructured database users. Relational Database brought into the relationship between data as well improved the performance of the data retrieval. Database world had immediately seen a major transformation and every single vendors and database users suddenly started to adopt the relational database models. Relational Database Management Systems Since Edgar F Codd proposed 12 rules for the RBDMS there were many different vendors who started them to build applications and tools to support the relationship between database. This was indeed a learning curve for many of the developer who had never worked before with the modeling of the database. However, as time passed by pretty much everybody accepted the relationship of the database and started to evolve product which performs its best with the boundaries of the RDBMS concepts. This was the best era for the databases and it gave the world extreme experts as well as some of the best products. The Entity Relationship model was also evolved at the same time. In software engineering, an Entity–relationship model (ER model) is a data model for describing a database in an abstract way. Enormous Data Growth Well, everything was going fine with the RDBMS in the database world. As there were no major challenges the adoption of the RDBMS applications and tools was pretty much universal. There was a race at times to make the developer’s life much easier with the RDBMS management tools. Due to the extreme popularity and easy to use system pretty much every data was stored in the RDBMS system. New age applications were built and social media took the world by the storm. Every organizations was feeling pressure to provide the best experience for their users based the data they had with them. While this was all going on at the same time data was growing pretty much every organization and application. Data Warehousing The enormous data growth now presented a big challenge for the organizations who wanted to build intelligent systems based on the data and provide near real time superior user experience to their customers. Various organizations immediately start building data warehousing solutions where the data was stored and processed. The trend of the business intelligence becomes the need of everyday. Data was received from the transaction system and overnight was processed to build intelligent reports from it. Though this is a great solution it has its own set of challenges. The relational database model and data warehousing concepts are all built with keeping traditional relational database modeling in the mind and it still has many challenges when unstructured data was present. Interesting Challenge Every organization had expertise to manage structured data but the world had already changed to unstructured data. There was intelligence in the videos, photos, SMS, text, social media messages and various other data sources. All of these needed to now bring to a single platform and build a uniform system which does what businesses need. The way we do business has also been changed. There was a time when user only got the features what technology supported, however, now users ask for the feature and technology is built to support the same. The need of the real time intelligence from the fast paced data flow is now becoming a necessity. Large amount (Volume) of difference (Variety) of high speed data (Velocity) is the properties of the data. The traditional database system has limits to resolve the challenges this new kind of the data presents. Hence the need of the Big Data Science. We need innovation in how we handle and manage data. We need creative ways to capture data and present to users. Big Data is Reality! Tomorrow In tomorrow’s blog post we will try to answer discuss Basics of Big Data Architecture. 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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  • SQL SERVER – TechEd India 2012 – Content, Speakers and a Lots of Fun

    - by pinaldave
    TechEd is one event which every developers and IT professionals are looking forward to attend. It is opportunity of life time and no matter how many time one gets chance to engage with it, it is never enough. I still remember every single moment of every TechEd I have attended so far. We are less than 100 hours away from TechEd India 2012 event.This event is the one must attend event for every Technology Enthusiast. Fourth time in the row I am going to attend this event and I am equally excited as the first time of the event. There are going to be two very solid SQL Server track this time and I will be attending end of the end both the tracks. Here is my view on each of the 10 sessions. Each session is carefully crafted and leading exeprts from industry will present it. Day 1, March 21, 2012 T-SQL Rediscovered with SQL Server 2012 – This session is going to bring some of the lesser known enhancements that were brought with SQL Server 2012. When I learned that Jacob Sebastian is going to do this session my reaction to this is DEMO, DEMO and DEMO! Jacob spends hours and hours of his time preparing his session and this will be one of those session that I am confident will be delivered over and over through out the next many events. Catapult your data with SQL Server 2012 Integration Services – Praveen is expert story teller and one of the wizard when it is about SQL Server and business intelligence. He is surely going to mesmerize you with some interesting insights on SSIS performance too. Processing Big Data with SQL Server 2012 and Hadoop – There are three sessions on Big Data at TechEd India 2012. Stephen is going to deliver one of the session. Watching Stephen present is always joy and quite entertaining. He shares knowledge with his typical humor which captures ones attention. I wrote about what is BIG DATA in a blog post. SQL Server Misconceptions and Resolutions – I will be presenting this Session along with Vinod Kumar. READ MORE HERE. Securing with ContainedDB in SQL Server 2012 – Pranab is expert when it is about SQL Server and Security. I have seen him presenting and he is indeed very pleasant to watch. A dry subject like security, he makes it much lively. A Contained Database is a database which contains all the necessary settings and metadata, making database easily portable to another server. This database will contain all the necessary details and will not have to depend on any server where it is installed for anything. You can take this database and move it to another server without having any worries. Day 3, March 23, 2012 Peeling SQL Server like an Onion: Internals Demystified – Vinod Kumar has been writing about this extensively on his other blog post. In recent conversation he suggested that he will be creating very exclusive content for this presentation. I know Vinod for long time and have worked with him along many community activities. I am going to pay special attention to the details. I know Vinod has few give-away planned now for attending the session now only if he shares with us. Speed Up – Parallel Processes and unparalleled Performance – Performance tuning is my favorite subject. I will be discussing effect of parallelism on performance in this session. Here me out, there will be lots of quiz questions during this session and if you get the answers correct – you can win some really cool goodies – I Promise! READ MORE HERE. Keep your database available – AlwaysOn – Balmukund is like an army man. He is always ready to show and prove that he has coolest toys in terms of SQL Server and he knows how to keep them running AlwaysON. Availability groups, Listener, Clustering, Failover, Read-Only replica etc all will be demo’ed in this session. This is really heavy but very interesting content not to be missed. Lesser known facts about SQL Server Backup and Restore – Amit Banerjee – this name is known internationally for solving SQL Server problems in 140 characters. He has already blogged about this and this topic is going to be interesting. A successful restore strategy for applications is as good as their last good known backup. I have few difficult questions to ask to Amit and I am very sure that his unique style will entertain people. By the way, his one of the slide may give few in audience a funny heart attack. Top 5 reasons why you want SQL Server 2012 BI – Praveen plans to take a tour of some of the BI enhancements introduced in the new version. Business Insights with SQL Server is a critical building block and this version of SQL Server is no exception. For the matter of the fact, when I saw the demos he was going to show during this session, I felt like that I wish I can set up all of this on my machine. If you miss this session – you will miss one of the most informative session of the day. Also TechEd India 2012 has a Live streaming of some content and this can be watched here. The TechEd Team is planning to have some really good exclusive content in this channel as well. If you spot me, just do not hesitate to come by me and introduce yourself, I want to remember you! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLServer, T SQL, Technology Tagged: TechEd, TechEdIn

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  • Big Data – Various Learning Resources – How to Start with Big Data? – Day 20 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned how to become a Data Scientist for Big Data. In this article we will go over various learning resources related to Big Data. In this series we have covered many of the most essential details about Big Data. At the beginning of this series, I have encouraged readers to send me questions. One of the most popular questions is - “I want to learn more about Big Data. Where can I learn it?” This is indeed a great question as there are plenty of resources out to learn about Big Data and it is indeed difficult to select on one resource to learn Big Data. Hence I decided to write here a few of the very important resources which are related to Big Data. Learn from Pluralsight Pluralsight is a global leader in high-quality online training for hardcore developers.  It has fantastic Big Data Courses and I started to learn about Big Data with the help of Pluralsight. Here are few of the courses which are directly related to Big Data. Big Data: The Big Picture Big Data Analytics with Tableau NoSQL: The Big Picture Understanding NoSQL Data Analysis Fundamentals with Tableau I encourage all of you start with this video course as they are fantastic fundamentals to learn Big Data. Learn from Apache Resources at Apache are single point the most authentic learning resources. If you want to learn fundamentals and go deep about every aspect of the Big Data, I believe you must understand various concepts in Apache’s library. I am pretty impressed with the documentation and I am personally referencing it every single day when I work with Big Data. I strongly encourage all of you to bookmark following all the links for authentic big data learning. Haddop - The Apache Hadoop® project develops open-source software for reliable, scalable, distributed computing. Ambari: A web-based tool for provisioning, managing, and monitoring Apache Hadoop clusters which include support for Hadoop HDFS, Hadoop MapReduce, Hive, HCatalog, HBase, ZooKeeper, Oozie, Pig and Sqoop. Ambari also provides a dashboard for viewing cluster health such as heat maps and ability to view MapReduce, Pig and Hive applications visually along with features to diagnose their performance characteristics in a user-friendly manner. Avro: A data serialization system. Cassandra: A scalable multi-master database with no single points of failure. Chukwa: A data collection system for managing large distributed systems. HBase: A scalable, distributed database that supports structured data storage for large tables. Hive: A data warehouse infrastructure that provides data summarization and ad hoc querying. Mahout: A Scalable machine learning and data mining library. Pig: A high-level data-flow language and execution framework for parallel computation. ZooKeeper: A high-performance coordination service for distributed applications. Learn from Vendors One of the biggest issues with about learning Big Data is setting up the environment. Every Big Data vendor has different environment request and there are lots of things require to set up Big Data framework. Many of the users do not start with Big Data as they are afraid about the resources required to set up framework as well as a time commitment. Here Hortonworks have created fantastic learning environment. They have created Sandbox with everything one person needs to learn Big Data and also have provided excellent tutoring along with it. Sandbox comes with a dozen hands-on tutorial that will guide you through the basics of Hadoop as well it contains the Hortonworks Data Platform. I think Hortonworks did a fantastic job building this Sandbox and Tutorial. Though there are plenty of different Big Data Vendors I have decided to list only Hortonworks due to their unique setup. Please leave a comment if there are any other such platform to learn Big Data. I will include them over here as well. Learn from Books There are indeed few good books out there which one can refer to learn Big Data. Here are few good books which I have read. I will update the list as I will learn more. Ethics of Big Data Balancing Risk and Innovation Big Data for Dummies Head First Data Analysis: A Learner’s Guide to Big Numbers, Statistics, and Good Decisions If you search on Amazon there are millions of the books but I think above three books are a great set of books and it will give you great ideas about Big Data. Once you go through above books, you will have a clear idea about what is the next step you should follow in this series. You will be capable enough to make the right decision for yourself. Tomorrow In tomorrow’s blog post we will wrap up this series of 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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  • SQLAuthority News – #SQLPASS 2012 Seattle Update – Memorylane 2009, 2010, 2011

    - by pinaldave
    Today is the first day of the SQLPASS 2012 and I will be soon posting SQL Server 2012 experience over here. Today when I landed in Seattle, I got the nostalgia feeling. I used to stay in the USA. I stayed here for more than 7 years – I studied here and I worked in USA. I had lots of friends in Seattle when I used to stay in the USA. I always wanted to visit Seattle because it is THE place. I remember once I purchased a ticket to travel to Seattle through Priceline (well it was the cheapest option and I was a student) but could not fly because of an interesting issue. I used to be Teaching Assistant of an advanced course and the professor asked me to build a pop-quiz for the course. I unfortunately had to cancel the trip. Before I returned to India – I pretty much covered every city existed in my list to must visit, except one – Seattle. It was so interesting that I never made it to Seattle even though I wanted to visit, when I was in USA. After that one time I never got a chance to travel to Seattle. After a few years I also returned to India for good. Once on Television I saw “Sleepless in Seattle” movie playing and I immediately changed the channel as it reminded me that I never made it to Seattle before. However, destiny has its own way to handle decisions. After I returned to India – I visited Seattle total of 5 times and this is my 6th visit to Seattle in less than 3 years. I was here for 3 previous SQLPASS events – 2009, 2010, and 2011 as well two Microsoft Most Valuable Professional Summit in 2009 and 2010. During these five trips I tried to catch up with all of my all friends but I realize that time has its own way of doing things. Many moved out of Seattle and many were too busy revive the old friendship but there were few who always make a point to meet me when I travel to the city. During the course of my visits I have made few fantastic new friends – Rick Morelan (Joes 2 Pros) and Greg Lynch. Every time I meet them I feel that I know them for years. I think city of Seattle has played very important part in our relationship that I got these fantastic friends. SQLPASS is the event where I find all of my SQL Friends and I look for this event for an entire year. This year’s my goal is to meet as many as new friends I can meet. If you are going to be at SQLPASS – FIND ME. I want to have a photo with you. I want to remember each name as I believe this is very important part of our life – making new friends and sustaining new friendship. Here are few of the pointers where you can find me. All Keynotes – Blogger’s Table Exhibition Booth Joes 2 Pros Booth #117 – Do not forget to stop by at the booth – I might have goodies for you – limited editions. Book Signing Events – Check details in tomorrow’s blog or stop by Booth #117 Evening Parties 6th Nov – Welcome Reception Evening Parties 7th Nov - Exhibitor Reception – Do not miss Booth #117 Evening Parties 8th Nov - Community Appreciation Party Additionally at few other locations – Embarcadero Booth In Coffee shops in Convention Center If you are SQLPASS – make sure that I find an opportunity to meet you at the event. Reserve a little time and lets have a coffee together. I will be continuously tweeting about my where about on twitter so let us stay connected on twitter. Here is my experience of my earlier experience of attending SQLPASS. SQLAuthority News – Book Signing Event – SQLPASS 2011 Event Log SQLAuthority News – Meeting SQL Friends – SQLPASS 2011 Event Log SQLAuthority News – Story of Seattle – SQLPASS 2011 Event Log SQLAuthority News – SQLPASS Nov 8-11, 2010-Seattle – An Alternative Look at Experience SQLAuthority News – Notes of Excellent Experience at SQL PASS 2009 Summit, Seattle Let us meet! Reference: Pinal Dave (http://blog.SQLAuthority.com)   Filed under: PostADay, SQL, SQL Authority, SQL PASS, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

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  • SQLAuthority News – #TechEdIn – TechEd India 2012 Memories and Photos

    - by pinaldave
    TechEd India 2012 was held in Bangalore last March 21 to 23, 2012. Just like every year, this event is bigger, grander and inspiring. Pinal Dave at TechEd India 2012 Family Event Every single year, TechEd is a special affair for my entire family.  Four months before the start of TechEd, I usually start to build the mental image of the event. I start to think  about various things. For the most part, what excites me most is presenting a session and meeting friends. Seriously, I start thinking about presenting my session 4 months earlier than the event!  I work on my presentation day and night. I want to make sure that what I present is accurate and that I have experienced it firsthand. My wife and my daughter also contribute to my efforts. For us, TechEd is a family event, and the two of them feel equally responsible as well. They give up their family time so I can bring out the best content for the Community. Pinal, Shaivi and Nupur at TechEd India 2012 Guinea Pigs (My Experiment Victims) I do not rehearse my session, ever. However, I test my demo almost every single day till the last moment that I have to present it already. I sometimes go over the demo more than 2-3 times a day even though the event is more than a month away. I have two “guinea pigs”: 1) Nupur Dave and 2) Vinod Kumar. When I am at home, I present my demos to my wife Nupur. At times I feel that people often backup their demo, but in my case, I have backup demo presenters. In the office during lunch time, I present the demos to Vinod. I am sure he can walk my demos easily with eyes closed. Pinal and Vinod at TechEd India 2012 My Sessions I’ve been determined to present my sessions in a real and practical manner. I prefer to present the subject that I myself would be eager to attend to and sit through if I were an audience. Just keeping that principle in mind, I have created two sessions this year. SQL Server Misconception and Resolution Pinal and Vinod at TechEd India 2012 We believe all kinds of stuff – that the earth is flat, or that the forbidden fruit is apple, or that the big bang theory explains the origin of the universe, and so many other things. Just like these, we have plenty of misconceptions in SQL Server as well. I have had this dream of co-presenting a session with Vinod Kumar for the past 3 years. I have been asking him every year if we could present a session together, but we never got it to work out, until this year came. Fortunately, we got a chance to stand on the same stage and present a single subject.  I believe that Vinod Kumar and I have an excellent synergy when we are working together. We know each other’s strengths and weakness. We know when the other person will speak and when he will keep quiet. The reason behind this synergy is that we have worked on 2 Video Learning Courses (SQL Server Indexes and SQL Server Questions and Answers) and authored 1 book (SQL Server Questions and Answers) together. Crowd Outside Session Hall This session was inspired from the “Laurel and Hardy” show so we performed a role-playing of those famous characters. We had an excellent time at the stage and, for sure, the audience had a wonderful time, too. We had an extremely large audience for this session and had a great time interacting with them. Speed Up! – Parallel Processes and Unparalleled Performance Pinal Dave at TechEd India 2012 I wanted to approach this session at level 400 and I was very determined to do so. The biggest challenge I had was that this was a total of 60 minutes of session and the audience profile was very generic. I had to present at level 100 as well at 400. I worked hard to tune up these demos. I wanted to make sure that my messages would land perfectly to the minds of the attendees, and when they walk out of the session, they could use the knowledge I shared on their servers. After the session, I felt an extreme satisfaction as I received lots of positive feedback at the event. At one point, so many people rushed towards me that I was a bit scared that the stage might break and someone would get injured. Fortunately, nothing like that happened and I was able to shake hands with everybody. Pinal Dave at TechEd India 2012 Crowd rushing to Pinal at TechEd India 2012 Networking This is one of the primary reasons many of us visit the annual TechEd event. I had a fantastic time meeting SQL Server enthusiasts. Well, it was a terrific time meeting old friends, user group members, MVPs and SQL Enthusiasts. I have taken many photographs with lots of people, but I have received a very few back. If you are reading this blog and have a photo of us at the event, would you please send it to me so I could keep it in my memory lane? SQL Track Speaker: Jacob and Pinal at TechEd India 2012 SQL Community: Pinal, Tejas, Nakul, Jacob, Balmukund, Manas, Sudeepta, Sahal at TechEd India 2012 Star Speakers: Amit and Balmukund at TechEd India 2012 TechED Rockstars: Nakul, Tejas and Pinal at TechEd India 2012 I guess TechEd is a mix of family affair and culture for me! Hamara TechEd (Our TechEd) Please tell me which photo you like the most! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLAuthority News, SQLServer, T SQL, Technology Tagged: TechEd, TechEdIn

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  • SQLAuthority News – #TechEDIn – TechEd India 2012 – Things to Do and Explore for SQL Enthusiast

    - by pinaldave
    TechEd India 2012 is just 48 hours away and I have been receiving lots of requests regarding how SQL enthusiasts can maximize their time they’ll be spending at TechEd India 2012. Trust me – TechEd is the biggest Tech Event in India and it is much larger in magnitude than we can imagine. There are plenty of tracks there and lots of things to do. Honestly, we need clone ourselves multiple times to completely cover the event. However, I am going to talk about SQL enthusiasts only right now. In this post, I’ll share a few things they can do in this big event. But before I start talking about specific things, there is one thing which is a must – Keynote. There are amazing Keynotes planned every single day at TechEd India 2012. One should not miss them at all. Social Media I am a big believer of the social media. I am everywhere - Twitter, Facebook, LinkedIn and GPlus. I suggest you follow the tag #TechEdIn as well as contribute at the healthy conversation going on right now. You may want to follow a few of the SQL Server enthusiasts who are also attending events like TechEd India. This way, you will know where they are and you can contribute along with them. For a good start, you can follow all the speakers who are presenting at the event. I have linked all the speakers’ names with their respective Twitter accounts. Networking Do not stop meeting new people. Introduce yourself. Catch the speakers after their sessions. Meet other SQL experts and discuss SQL as well as life aside SQL. The best way to start the communication is to talk about something new. Here are a few lines I usually use when I have to break the ice: SQL Server 2012 is just released and I have installed it. How many SQL Server sessions are you going to attend? I am going to attend _________ I am a big fan of SQL Server. Sessions Agenda Day 1 T-SQL Rediscovered with SQL Server 2012 - Jacob Sebastian Catapult your data with SQL Server 2012 integration services - Praveen Srivatsa Processing Big Data with SQL Server 2012 and Hadoop  - Stephan Forte SQL Server Misconceptions and Resolution – A Practical Perspective – Pinal Dave and Vinod Kumar Securing with ContainedDB in SQL Server 2012  - Pranab Majumdar Agenda Day 2 Hand-on-Lab – Exploring Power View with SQL Server 2012 – Ravi S. Maniam Hand-on-Lab - SQL Server 2012 – AlwaysOn Availability Groups  - Amit Ganguli Agenda Day 3 Peeling SQL Server like an Onion: Internals Debunked  - Vinod Kumar Speed Up! – Parallel Processes and Unparalleled Performance  - Pinal Dave Keeping Your Database Available – ‘AlwaysOn’  - Balmukund Lakhani Lesser Known Facts of SQL Server Backup and Restore  - Amit Banerjee Top five reasons why you want SQL Server 2012 BI - Praveen Srivatsa Product Booth and Event Partners There will be a dedicated SQL Server booth at the event. I suggest you stop by there and do communication with SQL Server Experts. Additionally there will be booths of various event partners. Stop by their booth and see if they have a product which can help your career. I know that Pluralsight has recently released my course on their online learning site and if that interests you, you can talk about the subject with them. Bring Your Camera Make a list of the people you want to meet. Follow them on Twitter or send them an email and know their location. Introduce yourself, meet them and have your conversation. Do not forget to take a photo with them and later on, share the photo on social media. It would be nice to send an email to everyone with attached high resolution images if you have their email address. After-hours parties After-hours parties are not always about eating and meeting friends but sometimes, they are very informative. Last time I ended up meeting an SQL expert, and we end up talking for long hours on various aspects of SQL Server. After 4 hours, we figured out that he stays in the same apartment complex as mine and since we have had an excellent friendship, he has then become our family friend. So, my advice is that you start to seek out who is meeting where in the evening and see if you can get invited to the parties. Make new friends but never lose mutual respect by doing something silly. Meet Me I will be at the event for three days straight. I will be around the SQL tracks. Please stop by and introduce yourself. I would like to meet you and talk to you. Meeting folks from the Community is very important as we all speak the same language at the end of the day – SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology

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  • SQL SERVER – What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1

    - by Pinal Dave
    This is the first part of the series Incremental Statistics. Here is the index of the complete series. What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1 Simple Example of Incremental Statistics – Performance improvements in SQL Server 2014 – Part 2 DMV to Identify Incremental Statistics – Performance improvements in SQL Server 2014 – Part 3 Statistics are considered one of the most important aspects of SQL Server Performance Tuning. You might have often heard the phrase, with related to performance tuning. “Update Statistics before you take any other steps to tune performance”. Honestly, I have said above statement many times and many times, I have personally updated statistics before I start to do any performance tuning exercise. You may agree or disagree to the point, but there is no denial that Statistics play an extremely vital role in the performance tuning. SQL Server 2014 has a new feature called Incremental Statistics. I have been playing with this feature for quite a while and I find that very interesting. After spending some time with this feature, I decided to write about this subject over here. New in SQL Server 2014 – Incremental Statistics Well, it seems like lots of people wants to start using SQL Server 2014′s new feature of Incremetnal Statistics. However, let us understand what actually this feature does and how it can help. I will try to simplify this feature first before I start working on the demo code. Code for all versions of SQL Server Here is the code which you can execute on all versions of SQL Server and it will update the statistics of your table. The keyword which you should pay attention is WITH FULLSCAN. It will scan the entire table and build brand new statistics for you which your SQL Server Performance Tuning engine can use for better estimation of your execution plan. UPDATE STATISTICS TableName(StatisticsName) WITH FULLSCAN Who should learn about this? Why? If you are using partitions in your database, you should consider about implementing this feature. Otherwise, this feature is pretty much not applicable to you. Well, if you are using single partition and your table data is in a single place, you still have to update your statistics the same way you have been doing. If you are using multiple partitions, this may be a very useful feature for you. In most cases, users have multiple partitions because they have lots of data in their table. Each partition will have data which belongs to itself. Now it is very common that each partition are populated separately in SQL Server. Real World Example For example, if your table contains data which is related to sales, you will have plenty of entries in your table. It will be a good idea to divide the partition into multiple filegroups for example, you can divide this table into 3 semesters or 4 quarters or even 12 months. Let us assume that we have divided our table into 12 different partitions. Now for the month of January, our first partition will be populated and for the month of February our second partition will be populated. Now assume, that you have plenty of the data in your first and second partition. Now the month of March has just started and your third partition has started to populate. Due to some reason, if you want to update your statistics, what will you do? In SQL Server 2012 and earlier version You will just use the code of WITH FULLSCAN and update the entire table. That means even though you have only data in third partition you will still update the entire table. This will be VERY resource intensive process as you will be updating the statistics of the partition 1 and 2 where data has not changed at all. In SQL Server 2014 You will just update the partition of Partition 3. There is a special syntax where you can now specify which partition you want to update now. The impact of this is that it is smartly merging the new data with old statistics and update the entire statistics without doing FULLSCAN of your entire table. This has a huge impact on performance. Remember that the new feature in SQL Server 2014 does not change anything besides the capability to update a single partition. However, there is one feature which is indeed attractive. Previously, when table data were changed 20% at that time, statistics update were triggered. However, now the same threshold is applicable to a single partition. That means if your partition faces 20% data, change it will also trigger partition level statistics update which, when merged to your final statistics will give you better performance. In summary If you are not using a partition, this feature is not applicable to you. If you are using a partition, this feature can be very helpful to you. Tomorrow: We will see working code of SQL Server 2014 Incremental Statistics. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SQL Statistics, Statistics

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  • SQLAuthority Guest Post – Lessons from Life and Work by Srini Chandra (Author of 3 Lives, in search of bliss)

    - by pinaldave
    Work and life are confusing terms together. How can one consider work outside of life. Work should be part of life or are we considering ourselves dead when we are at work. I have often seen developers and DBA complaining and confused about their job, work and life. Complaining is easy and everyone can do. I have heard quite often expression – “I do not have any other option.” I requested Srini Chanda (renowned author of Amazon Best Seller 3 Lives, in search of bliss (Amazon | Flipkart) to write a guest post on this subject which developer can read and appreciate. Let us see Srini’s thoughts in his own words. Each of us who works in the technology industry carries an especially heavy burden nowadays. For, fate has placed in our hands an awesome power to shape our society and its consciousness. For that reason, we must pay more and more attention to issues of professionalism, social responsibility and ethics. Equally importantly, the responsibility lies in our hands to ensure that we view our work and career as an opportunity to enlighten and lift ourselves up. Story: A Prisoner, 20 years and a Wheel Many years ago, I heard this story from a professor when I was a student at Carnegie Mellon. A man was sentenced to 20 years in prison. During his time in prison, he was asked to turn a wheel every day. So, every day he turned the wheel. At times, when he was tired or puzzled and stopped turning the wheel, he would be flogged with a whip. The man did not know anything about the wheel other than that it was placed outside his jail somewhere. He wondered if the wheel crushed corn or if it ground wheat or something similar. He wondered if turning the wheel was useful to anyone. At the end of his jail term, he rushed out to see what the wheel was doing. To his disappointment, he found that the wheel was not connected to anything. All these years, he had been toiling for nothing. He gave a loud, frustrated shout and dropped dead. How many of us are turning wheels wondering what it is connected to? How many of us have unstated, uncaring attitudes towards our careers? How many of us view work as drudgery, as no more than a way to earn that next paycheck? How many of us have wondered about the spiritually uplifting aspect of work? Can a workforce that views work as merely a chore, be ethical? Can it produce truly life enhancing technology? Can it make positive contributions to the quality of life of a society? I think not. Thanks to Pinal and you, his readers, for giving me this opportunity to share my thoughts in a series of guest posts. I’d like to present a few ways over the next few weeks, in which we can tap into the liberating potential of work and make our lives better in the process. Now, please allow me to tell you another version of the story that the good professor shared with us in the classroom that day. Story: A Prisoner, 20 years, a Wheel and the LIFE A man was sentenced to 20 years in prison. During his time in prison, he was asked to turn a wheel every day. So, every day he turned the wheel. At first, his whole body and mind rebelled against his predicament. So, his limbs grew weary and his mind became numb and confused. And then, his self-awareness began to grow. He began to wonder how he came to be in the prison in the first place. He looked around and saw all his fellow prisoners also turning the wheel. His wife, his parents, his friends and his children – they were all in the prison too, and turning their own wheels! He began to wonder how this came about. As he wondered more and more, he began to focus less on his physical drudgery and boredom. And he began to clearly see his inner spirit which guided him in ways that allowed him to see the world with a universal view. His inner spirit guided him towards the source of eternal wisdom and happiness. He began to see the source of happiness in everything around him – his prison bound relationships, even his jailers and in his wheel. He became a source of light to those around him. His wheel jokes and humor infected them with joy and happiness. Finally, the day came for his release from jail. He walked calmly outside the jail and laughed aloud when he saw that the wheel was not connected to anything. He knelt down, kissed it and thanked it for the wisdom it taught him. Life is the prison. The wheel is your work. Both are sacred. Both have enormous powers to teach us wisdom and bring us happiness. Whether we allow them to do so, is a choice we have to make. Over the next few weeks, I hope to share with you a few lessons that I have learnt at the wheel in my two decades of my career (prison). Thank you for reading, and do let me know what you think. Reference: Srini Chandra (3 Lives, in search of bliss), Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Book Review, T SQL, Technology

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  • SQL SERVER – Recover the Accidentally Renamed Table

    - by pinaldave
    I have no answer to following question. I saw a desperate email marked as urgent delivered in my mailbox. “I accidentally renamed table in my SSMS. I was scrolling very fast and I made mistakes. It was either because I double clicked or clicked on F2 (shortcut key for renaming). However, I have made the mistake and now I have no idea how to fix this. I am in big trouble. Help me get my original tablename.” I have seen many similar scenarios in my life and they give me a very good opportunity to preach wisdom but when the house is burning, we cannot talk about how we should have conserved the water earlier. The goal at that point is to put off the fire as fast as we can. I decided to answer this email with my best knowledge. If you have renamed the table, I think you pretty much is out of luck. Here are few things which you can do which can give you idea about what your tablename can be if you are lucky. Method 1: (Not Recommended but try your luck) Check your naming convention of your system. I have often seen that many organizations name their index as IX_TableName_Colms or name their keys as FK_TableName1_TableName2_Cols. If your organization is following the same you can get the name from your table, you may refer your keys. Again, note that this is quite possible that your tablename was already renamed and your keys were not updated. This can easily lead you to select incorrect name. I think follow this if you are confident or move to the next method. Method 2: (Not Recommended but try your luck) This method is also based on your orgs naming convention. If you use the name of the table in any columnname (some organizations use tablename in their incremental identity column name), you can get that name from there. Method 3: (Not Recommended but try your luck) If you know where your table was used in your stored procedures, you can script your stored procedure and find the name of the table back. Method 4: (Try your luck) All the best organizations first create a data model of the schema and there is good chance that this table is used there, you should take your chances and refer original document. If your organization is good at managing docs or source code, you will get the name of the table back for sure. Method 5: (It WORKS but try on a development server) There is no sure way to get you the name of the table which you accidentally renamed however, there is one way which will work for sure. You need to take your latest full backup and restore it on your development server (remember not on production or where you have renamed this column). Now restore latest differential file of the full backup. Now restore all the log files one by one making sure that you are restoring before the point of time of you renamed the tablename. Now go to explore and this will give you the name of the table which you have renamed. If you are confident that the same table existed with the same name when the last full backup was made, you do not have to go to all the steps. You can just get the name of the table directly from last backup’s restore. Read the article about Backup Timeline. Wisdom: How can I miss to preach wisdom when I get the opportunity to do so? Here are a few points to remember. Use a different account to explore production environment. Do not use the same account which have all the rights and permissions all the time. Use the account which has read only permissions if there are no modification required. Use policy based management to prevent changes which are accidental. If there was policy of valid names, the accidental change of the table was not possible unless it was intentional delibarate changes. Have a proper auditing of the system in place. You can use DDL triggers but be careful with its usage (get it reviewed properly first). (Add your suggestion here) I guess Method 5 will work all the time (using point in time restore). Everything else is chance of luck and if you are lucky are bad – you will get further incorrect name. Now go back and read the first line of this blog. Out of five method four methods are just lucky guesses. The method 5 will work but again it is a lengthy process if the size of the database is huge or if you do not have full backup. Did I miss anything obvious? Please leave a comment and I will publish your answer with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Responsive Design: Media Query Bookmarket - shows the applied media queries and current window size

    - by ihaynes
    Originally posted on: http://geekswithblogs.net/ihaynes/archive/2013/06/19/153181.aspxThere are any number of tools for resizing the browser window to check responsive designs. One that stands out for me is the Media Query Bookmarklet from the Sparkbox Foundry. This shows you the currently applied media queries and browser size in both pixels and ems. Once you've used this you'll wonder how you managed without it.Note: The main page says in works in Chrome and Safari. It also works in IE10.Details at http://seesparkbox.com/foundry/media_query_bookmarklet

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  • SQLAuthority News – Great Time Spent at Great Indian Developers Summit 2014

    - by Pinal Dave
    The Great Indian Developer Conference (GIDS) is one of the most popular annual event held in Bangalore. This year GIDS is scheduled on April 22, 25. I will be presented total four sessions at this event and each session is very different from each other. Here are the details of four of my sessions, which I presented there. Pluralsight Shades This event was a great event and I had fantastic fun presenting a technology over here. I was indeed very excited that along with me, I had many of my friends presenting at the event as well. I want to thank all of you to attend my session and having standing room every single time. I have already sent resources in my newsletter. You can sign up for the newsletter over here. Indexing is an Art I was amazed with the crowd present in the sessions at GIDS. There was a great interest in the subject of SQL Server and Performance Tuning. Audience at GIDS I believe event like such provides a great platform to meet and share knowledge. Pinal at Pluralsight Booth Here are the abstract of the sessions which I had presented. They were recorded so at some point in time they will be available, but if you want the content of all the courses immediately, I suggest you check out my video courses on the same subject on Pluralsight. Indexes, the Unsung Hero Relevant Pluralsight Course Slow Running Queries are the most common problem that developers face while working with SQL Server. While it is easy to blame SQL Server for unsatisfactory performance, the issue often persists with the way queries have been written, and how Indexes has been set up. The session will focus on the ways of identifying problems that slow down SQL Server, and Indexing tricks to fix them. Developers will walk out with scripts and knowledge that can be applied to their servers, immediately post the session. Indexes are the most crucial objects of the database. They are the first stop for any DBA and Developer when it is about performance tuning. There is a good side as well evil side to indexes. To master the art of performance tuning one has to understand the fundamentals of indexes and the best practices associated with the same. We will cover various aspects of Indexing such as Duplicate Index, Redundant Index, Missing Index as well as best practices around Indexes. SQL Server Performance Troubleshooting: Ancient Problems and Modern Solutions Relevant Pluralsight Course Many believe Performance Tuning and Troubleshooting is an art which has been lost in time. However, truth is that art has evolved with time and there are more tools and techniques to overcome ancient troublesome scenarios. There are three major resources that when bottlenecked creates performance problems: CPU, IO, and Memory. In this session we will focus on High CPU scenarios detection and their resolutions. If time permits we will cover other performance related tips and tricks. At the end of this session, attendees will have a clear idea as well as action items regarding what to do when facing any of the above resource intensive scenarios. Developers will walk out with scripts and knowledge that can be applied to their servers, immediately post the session. To master the art of performance tuning one has to understand the fundamentals of performance, tuning and the best practices associated with the same. We will discuss about performance tuning in this session with the help of Demos. Pinal Dave at GIDS MySQL Performance Tuning – Unexplored Territory Relevant Pluralsight Course Performance is one of the most essential aspects of any application. Everyone wants their server to perform optimally and at the best efficiency. However, not many people talk about MySQL and Performance Tuning as it is an extremely unexplored territory. In this session, we will talk about how we can tune MySQL Performance. We will also try and cover other performance related tips and tricks. At the end of this session, attendees will not only have a clear idea, but also carry home action items regarding what to do when facing any of the above resource intensive scenarios. Developers will walk out with scripts and knowledge that can be applied to their servers, immediately post the session. To master the art of performance tuning one has to understand the fundamentals of performance, tuning and the best practices associated with the same. You will also witness some impressive performance tuning demos in this session. Hidden Secrets and Gems of SQL Server We Bet You Never Knew Relevant Pluralsight Course SQL Trio Session! It really amazes us every time when someone says SQL Server is an easy tool to handle and work with. Microsoft has done an amazing work in making working with complex relational database a breeze for developers and administrators alike. Though it looks like child’s play for some, the realities are far away from this notion. The basics and fundamentals though are simple and uniform across databases, the behavior and understanding the nuts and bolts of SQL Server is something we need to master over a period of time. With a collective experience of more than 30+ years amongst the speakers on databases, we will try to take a unique tour of various aspects of SQL Server and bring to you life lessons learnt from working with SQL Server. We will share some of the trade secrets of performance, configuration, new features, tuning, behaviors, T-SQL practices, common pitfalls, productivity tips on tools and more. This is a highly demo filled session for practical use if you are a SQL Server developer or an Administrator. The speakers will be able to stump you and give you answers on almost everything inside the Relational database called SQL Server. I personally attended the session of Vinod Kumar, Balmukund Lakhani, Abhishek Kumar and my favorite Govind Kanshi. Summary If you have missed this event here are two action items 1) Sign up for Resource Newsletter 2) Watch my video courses on Pluralsight Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: MySQL, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLAuthority News, T SQL Tagged: GIDS

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  • Responsive Design: Media query fix for IE10 on Windows Phone 8

    - by ihaynes
    Originally posted on: http://geekswithblogs.net/ihaynes/archive/2013/07/01/responsive-design-media-query-fix-for-ie10-on--windows.aspxThe version of IE10 on Windows Phone 8 apparently has a bug which results in media queries not seeing the correct device width.This post from Devhammer explains all.http://devhammer.net/responsive-design-fix-for-windows-phone-8-device-adaptationI'd not noticed this on the WP8 Emulator which proves yet again that testing on real devices is essential.

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  • SQL SERVER – Not Possible – Delete From Multiple Table – Update Multiple Table in Single Statement

    - by pinaldave
    There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? The answer is – No, You cannot and you should not. SQL Server does not support deleting or updating from two tables in a single update. If you want to delete or update two different tables – you may want to write two different delete or update statements for it. This method has many issues – from the consistency of the data to SQL syntax. Now here is the real reason for this blog post – yesterday I was asked this question again and I replied my canned answer saying it is not possible and it should not be any way implemented that day. In the response to my reply I was pointed out to my own blog post where user suggested that I had previously mentioned this is possible and with demo example. Let us go over my conversation – you may find it interesting. Let us call the user DJ. DJ: Pinal, can we delete multiple table in a single statement or with single delete statement? Pinal: No, you cannot and you should not. DJ: Oh okey, if that is the case, why do you suggest to do that? Pinal: (baffled) I am not suggesting that. I am rather suggesting that it is not possible and it should not be possible. DJ: Hmm… but in that case why did you blog about it earlier? Pinal: (What?) No, I did not. I am pretty confident. DJ: Well, I am confident as well. You did. Pinal: In that case, it is my word against your word. Isn’t it? DJ: I have proof. Do you want to see it that you suggest it is possible? Pinal: Yes, I will be delighted too. (After 10 Minutes) DJ: Here are not one but two of your blog posts which talks about it - SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2 Pinal: Oh! DJ: I know I was correct. Pinal: Well, oh man, I did not mean there what you mean here. DJ: I did not understand can you explain it further. Pinal: Here we go. The example in the other blog is the example of the cascading delete or cascading update. I think you may want to understand the concept of the foreign keys and cascading update/delete. The concept of cascading exists to maintain data integrity. If there primary keys get deleted the update or delete reflects on the foreign key table to maintain the key integrity and data consistency. SQL Server follows ANSI Entry SQL with regard to referential integrity between PrimaryKey and ForeignKey columns which requires the inserting, updating, and deleting of data in related tables to be restricted to values that preserve the integrity. This is all together different concept than deleting multiple values in a single statement. When I hear that someone wants to delete or update multiple table in a single statement what I assume is something very similar to following. DELETE/UPDATE Table 1 (cols) Table 2 (cols) VALUES … which is not valid statement/syntax as well it is not ASNI standards as well. I guess, after this discussion with DJ, I realize I need to do a blog post so I can add the link to this blog post in my canned answer. Well, it was a fun conversation with DJ and I hope it the message is very clear now. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2

    - by pinaldave
    Social media has created an Always Connected World for us. Recently I enrolled myself to learn new technologies as a student. I had decided to focus on learning and decided not to stay connected on the internet while I am in the learning session. On the second day of the event after the learning was over, I noticed lots of notification from my friend on my various social media handle. He had connected with me on Twitter, Facebook, Google+, LinkedIn, YouTube as well SMS, WhatsApp on the phone, Skype messages and not to forget with a few emails. I right away called him up. The problem was very unique – let us hear the problem in his own words. “Pinal – we are in big trouble we are not able to figure out what is going on. Our product details table is continuously loosing rows. Lots of rows have disappeared since morning and we are unable to find why the rows are getting deleted. We have made sure that there is no DELETE command executed on the table as well. The matter of the fact, we have removed every single place the code which is referencing the table. We have done so many crazy things out of desperation but no luck. The rows are continuously deleted in a random pattern. Do you think we have problems with intrusion or virus?” After describing the problems he had pasted few rants about why I was not available during the day. I think it will be not smart to post those exact words here (due to many reasons). Well, my immediate reaction was to get online with him. His problem was unique to him and his team was all out to fix the issue since morning. As he said he has done quite a lot out in desperation. I started asking questions from audit, policy management and profiling the data. Very soon I realize that I think this problem was not as advanced as it looked. There was no intrusion, SQL Injection or virus issue. Well, long story short first - It was a very simple issue of foreign key created with ON UPDATE CASCADE and ON DELETE CASCADE.  CASCADE allows deletions or updates of key values to cascade through the tables defined to have foreign key relationships that can be traced back to the table on which the modification is performed. ON DELETE CASCADE specifies that if an attempt is made to delete a row with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also deleted. ON UPDATE CASCADE specifies that if an attempt is made to update a key value in a row, where the key value is referenced by foreign keys in existing rows in other tables, all of the foreign key values are also updated to the new value specified for the key. (Reference: BOL) In simple words – due to ON DELETE CASCASE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. In my friend’s case, they had two tables, Products and ProductDetails. They had created foreign key referential integrity of the product id between the table. Now the as fall was up they were updating their catalogue. When they were updating the catalogue they were deleting products which are no more available. As the changes were cascading the corresponding rows were also deleted from another table. This is CORRECT. The matter of the fact, there is no error or anything and SQL Server is behaving how it should be behaving. The problem was in the understanding and inappropriate implementations of business logic.  What they needed was Product Master Table, Current Product Catalogue, and Product Order Details History tables. However, they were using only two tables and without proper understanding the relation between them was build using foreign keys. If there were only two table, they should have used soft delete which will not actually delete the record but just hide it from the original product table. This workaround could have got them saved from cascading delete issues. I will be writing a detailed post on the design implications etc in my future post as in above three lines I cannot cover every issue related to designing and it is also not the scope of the blog post. More about designing in future blog posts. Once they learn their mistake, they were happy as there was no intrusion but trust me sometime we are our own enemy and this is a great example of it. In tomorrow’s blog post we will go over their code and workarounds. Feel free to share your opinions, experiences and comments. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Professional Development – Difference Between Bio, CV and Resume

    - by Pinal Dave
    Applying for work can be very stressful – you want to put your best foot forward, and it can be very hard to sell yourself to a potential employer while highlighting your best characteristics and answering questions.  On top of that, some jobs require different application materials – a biography (or bio), a curriculum vitae (or CV), or a resume.  These things seem so interchangeable, so what is the difference? Let’s start with the one most of us have heard of – the resume.  A resume is a summary of your job and education history.  If you have ever applied for a job, you will have used a resume.  The ability to write a good resume that highlights your best characteristics and emphasizes your qualifications for a specific job is a skill that will take you a long way in the world.  For such an essential skill, unfortunately it is one that many people struggle with. RESUME So let’s discuss what makes a great resume.  First, make sure that your name and contact information are at the top, in large print (slightly larger font than the rest of the text, size 14 or 16 if the rest is size 12, for example).  You need to make sure that if you catch the recruiter’s attention and they know how to get a hold of you. As for qualifications, be quick and to the point.  Make your job title and the company the headline, and include your skills, accomplishments, and qualifications as bullet points.  Use good action verbs, like “finished,” “arranged,” “solved,” and “completed.”  Include hard numbers – don’t just say you “changed the filing system,” say that you “revolutionized the storage of over 250 files in less than five days.”  Doesn’t that sentence sound much more powerful? Curriculum Vitae (CV) Now let’s talk about curriculum vitae, or “CVs”.  A CV is more like an expanded resume.  The same rules are still true: put your name front and center, keep your contact info up to date, and summarize your skills with bullet points.  However, CVs are often required in more technical fields – like science, engineering, and computer science.  This means that you need to really highlight your education and technical skills. Difference between Resume and CV Resumes are expected to be one or two pages long – CVs can be as many pages as necessary.  If you are one of those people lucky enough to feel limited by the size constraint of resumes, a CV is for you!  On a CV you can expand on your projects, highlight really exciting accomplishments, and include more educational experience – including GPA and test scores from the GRE or MCAT (as applicable).  You can also include awards, associations, teaching and research experience, and certifications.  A CV is a place to really expand on all your experience and how great you will be in this particular position. Biography (Bio) Chances are, you already know what a bio is, and you have even read a few of them.  Think about the one or two paragraphs that every author includes in the back flap of a book.  Think about the sentences under a blogger’s photo on every “About Me” page.  That is a bio.  It is a way to quickly highlight your life experiences.  It is essentially the way you would introduce yourself at a party. Where a bio is required for a job, chances are they won’t want to know about where you were born and how many pets you have, though.  This is a way to summarize your entire job history in quick-to-read format – and sometimes during a job hunt, being able to get to the point and grab the recruiter’s interest is the best way to get your foot in the door.  Think of a bio as your entire resume put into words. Most bios have a standard format.  In paragraph one, talk about your most recent position and accomplishments there, specifically how they relate to the job you are applying for.  If you have teaching or research experience, training experience, certifications, or management experience, talk about them in paragraph two.  Paragraph three and four are for highlighting publications, education, certifications, associations, etc.  To wrap up your bio, provide your contact info and availability (dates and times). Where to use What? For most positions, you will know exactly what kind of application to use, because the job announcement will state what materials are needed – resume, CV, bio, cover letter, skill set, etc.  If there is any confusion, choose whatever the industry standard is (CV for technical fields, resume for everything else) or choose which of your documents is the strongest. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: About Me, PostADay, Professional Development, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • SQLAuthority News – A Conversation with an Old Friend – Sri Sridharan

    - by pinaldave
    Sri Sridharan is my old friend and we often talk on GTalk. The subject varies from Life in India/USA, movies, musics, and of course SQL. We have our differences when we talk about food or movie but we always agree when we talk about SQL. Yesterday while chatting with him we talked about SQLPASS and the conversation lasted for a long time. Here is the conversation between us on GTalk. I have removed a few of the personal talks and formatted into paragraphs as GTalk often shows stuff out of formatting. Pinal: Sri, Congrats on running for the PASS BoD again. You were so close last year. What made you decide to run again this year? Sri: Thank you Pinal for your leadership in the PASS India Community and all the things you do out there. After coming so close last year, there was no doubt in my mind that I will run again. I was truly humbled by the support I got from the community. Growing up in India for over 25 years, you are brought up in a very competitive part of the world. Right from the pressure of staying in the top of the class from kindergarten to your graduation, the relentless push from your parents about studying and getting good grades (and nothing else matters), you land up essentially living in a pressure cooker. To survive that relentless pressure, you need to have a thick skin, ability to stand up for who you really are , what you want to accomplish and in the process stay true those values. I am striving for a greater cause, to make PASS an organization that can help people with their SQL Server careers, to make PASS relevant to its chapter members, to make PASS an organization that every SQL professional in the world wants to be connected with. Just because I did not get elected or appointed last year does not mean that these causes are not worth fighting. Giving up upon failing the first time is simply not in me. If I did that, what message would I send to those who voted for me? What message would I send to my kids? Pinal: As someone who has such strong roots in India, what can the Indian PASS Community expect from you? Sri: First of all, I think fostering a regional leadership is something PASS must encourage as part of its global growth plan. For PASS global being able to understand all the issues in a region of the world and make sound decisions will be a tough thing to do on a continuous basis. I expect people like you, chapter leaders, regional mentors, MVPs of the region start playing a bigger role in shaping the next generation of PASS. That is something I said in my campaign and I still stand by it. I would like to see growth in the number of chapters in India. The current count does not truly represent the full potential of that region. I was pretty thrilled to see the Bangalore SQLSaturday happen early this year. I would like to see more of SQLSaturday events, at least in the major metro cities. I know the issues in India are very different from the rest of the world. So the formula needs to be tweaked a little for it to work better in India. Once the SQLSaturday model is vetted out, maybe there could be enough justification to have SQLRally India. PASS needs to have a premier SQL event in that region. Going to USA or Europe for that matter is incredibly hard due to VISA issues etc. So this could be a case of where PASS comes closer to where the community is. Pinal: What portfolio would take on if you are elected to the PASS Board? Sri: There are some very strong folks on the PASS Board today. The President discusses the portfolios with the group and makes the final call on the portfolios. I am also a fan of having a team associated with the portfolios. In that case, one person is the primary for a portfolio but secondary on a couple of other portfolios. This way people on the board have a direct vested interest in a few portfolios. Personally, I know I would these portfolios good justice – Chapters, Global Growth and Events (SQLSat, SQLRally). I would try to see if we can get a director to focus on Volunteers.  To me that is very critical for growth in the international regions. Pinal: This is an interesting conversation with you Sri. I know you so long time but this is indeed inspiring to many. India is a big country and we appreciate your thoughts. Sri: Thank you very much for taking time to chat with me today. Cheers. There are pretty strong candidates for SQLPASS Board of Elections this year. I know all of them in person and honestly it is going to be extremely difficult to not to vote for anybody. I am indeed in a crunch right now how to pick one over another. Though the choice is difficult, I encourage you to vote for them. I am extremely confident that the new board of directors will all have the same goal – Better SQL Server Community. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, DBA, PostADay, SQL, SQL Authority, SQL PASS, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

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  • Simple Query tuning with STATISTICS IO and Execution plans

    A great deal can be gleaned from the use of the STATISTICS IO and the execution plan, when you are checking that a query is performing properly. Josef Richberg, the current holder of the 'Exceptional DBA' award, explains how an apparently draconian IT policy turns out to be a useful ways of ensuring that Stored Procedures are carefully checked for performance before they are released

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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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