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• PASS Business Intelligence Virtual Chapter Upcoming Sessions (November 2013)

  - by Sergio Govoni

  Let me point out the upcoming live events, dedicated to Business Intelligence with SQL Server, that PASS Business Intelligence Virtual Chapter has scheduled for November 2013. The "Accidental Business Intelligence Project Manager"Date: Thursday 7th November - 8:00 PM GMT / 3:00 PM EST / Noon PSTSpeaker: Jen StirrupURL: https://attendee.gotowebinar.com/register/5018337449405969666 You've watched the Apprentice with Donald Trump and Lord Alan Sugar. You know that the Project Manager is usually the one gets firedYou've heard that Business Intelligence projects are prone to failureYou know that a quick Bing search for "why do Business Intelligence projects fail?" produces a search result of 25 million hits!Despite all this… you're now Business Intelligence Project Manager – now what do you do?In this session, Jen will provide a "sparks from the anvil" series of steps and working practices in Business Intelligence Project Management. What about waterfall vs agile? What is a Gantt chart anyway? Is Microsoft Project your friend or a problematic aspect of being a BI PM? Jen will give you some ideas and insights that will help you set your BI project right: assess priorities, avoid conflict, empower the BI team and generally deliver the Business Intelligence project successfully! Dimensional Modelling Design Patterns: Beyond BasicsDate: Tuesday 12th November - Noon AEDT / 1:00 AM GMT / Monday 11th November 5:00 PM PSTSpeaker: Jason Horner, Josh Fennessy and friendsURL: https://attendee.gotowebinar.com/register/852881628115426561 This session will provide a deeper dive into the art of dimensional modeling. We will look at the different types of fact tables and dimension tables, how and when to use them. We will also some approaches to creating rich hierarchies that make reporting a snap. This session promises to be very interactive and engaging, bring your toughest Dimensional Modeling quandaries. Data Vault Data Warehouse ArchitectureDate: Tuesday 19th November - 4:00 PM PST / 7 PM EST / Wednesday 20th November 11:00 PM AEDTSpeaker: Jeff Renz and Leslie WeedURL: https://attendee.gotowebinar.com/register/1571569707028142849 Data vault is a compelling architecture for an enterprise data warehouse using SQL Server 2012. A well designed data vault data warehouse facilitates fast, efficient and maintainable data integration across business systems. In this session Leslie and I will review the basics about enterprise data warehouse design, introduce you to the data vault architecture and discuss how you can leverage new features of SQL Server 2012 help make your data warehouse solution provide maximum value to your users. 

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• SQL query. An unusual join. DB implemented in sqlite-3

  - by user02814

  This is essentially a question about constructing an SQL query. The db is implemented with sqlite3. I am a relatively new user of SQL. I have two tables and want to join them in an unusual way. The following is an example to explain the problem. Table 1 (t1): id year name ------------------------- 297 2010 Charles 298 2011 David 300 2010 Peter 301 2011 Richard Table 2 (t2) id year food --------------------------- 296 2009 Bananas 296 2011 Bananas 297 2009 Melon 297 2010 Coffee 297 2012 Cheese 298 2007 Sugar 298 2008 Cereal 298 2012 Chocolate 299 2000 Peas 300 2007 Barley 300 2011 Beans 300 2012 Chickpeas 301 2010 Watermelon I want to join the tables on id and year. The catch is that (1) id must match exactly, but if there is no exact match in Table 2 for the year in Table 1, then I want to choose the year that is the next (lower) available. A selection of the kind that I want to produce would give the following result id year matchyr name food ------------------------------------------------- 297 2010 2010 Charles Coffee 298 2011 2008 David Cereal 300 2010 2007 Peter Barley 301 2011 2010 Richard Watermelon To summarise, id=297 had an exact match for year=2010 given in Table 1, so the corresponding line for id=297, year=2010 is chosen from Table 2. id=298, year=2011 did not have a matching year in Table 2, so the next available year (less than 2011) is chosen. As you can see, I would also like to know what that matched year (whether exactly , or inexactly) actually was. I would very much appreciate (1) an indication (yes/no answer) of whether this is possible to do in SQL alone, or whether I need to look outside SQL, and (2) a solution, if that is not too onerous.

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• Project Gantt chart using ADF BC

  - by shantala.sankeshwar

  This article describes simple example of using Project Gantt chart using ADF Business components.Use Case DescriptionLet us create a simple Project Gantt chart using ADF Business components & try to get the selected tasks details. Implementation stepsA project Gantt chart is used for project management. The chart lists tasks vertically and shows the duration of each task as a bar on a horizontal time line.To create a basic project gantt chart,we first need to define  2 tables as below:1)task_table with taskid,task_type,start_date & end_date 2)subtask_table with subtaskid,subtask_type,start_date, end_date &  taskidNow we can create Business components for the above 2 tables .Then we will create new jspx page -projectGantt.jspx Drop TaskView1 as Gantt->Project: Select all required columns under tasks & subtasks tabs of 'create Project Gantt chart' dialog.We have created Project Gantt chart that lists tasks & its subtasks.Now if we need to get all task details selected by the user then define taskSelectionListener for the dvt:projectGantt in jspx source page: taskSelectionListener="#{test.taskSelectlistener}" public void taskListener(TaskSelectionEvent taskSelectionEvent) {// This codes gives all the tasks selected by user System.out.println("Selected task details +taskSelectionEvent.getTask());            }Run the above page & note that it shows all details of tasks nodes & expanding these tasks nodes shows its corresponding subtasks details.Now if user selects 2 tasks,we can see that it prints the complete task details for the selected tasks.

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• What am I doing wrong in my config for MySql?

  - by Knight Hawk3

  When I load my my.conf with the config at the bottom Mysql fails to start and prints no errors. I am running Arch Linux (Updated) with the latest MySQL (5.5) and the latest nginx (Well latest in the repository, Not sure how to check. Only installed it today) I will give you any info you ask for. Thanks for helping! # The following options will be passed to all MySQL clients [client] #password = your_password port = 3306 socket = /var/run/mysqld/mysqld.sock # Here follows entries for some specific programs # The MySQL server [mysqld] port = 3306 socket = /var/run/mysqld/mysqld.sock skip-locking key_buffer = 16K max_allowed_packet = 1M table_cache = 4 sort_buffer_size = 64K read_buffer_size = 256K read_rnd_buffer_size = 256K net_buffer_length = 2K thread_stack = 64K # Don’t listen on a TCP/IP port at all. This can be a security enhancement, # if all processes that need to connect to mysqld run on the same host. # All interaction with mysqld must be made via Unix sockets or named pipes. # Note that using this option without enabling named pipes on Windows # (using the “enable-named-pipe” option) will render mysqld useless! # #skip-networking server-id = 1 # Uncomment the following if you want to log updates #log-bin=mysql-bin # Uncomment the following if you are NOT using BDB tables skip-bdb # Uncomment the following if you are using InnoDB tables #innodb_data_home_dir = /var/lib/mysql/ #innodb_data_file_path = ibdata1:10M:autoextend #innodb_log_group_home_dir = /var/lib/mysql/ #innodb_log_arch_dir = /var/lib/mysql/ # You can set .._buffer_pool_size up to 50 – 80 % # of RAM but beware of setting memory usage too high #innodb_buffer_pool_size = 16M #innodb_additional_mem_pool_size = 2M # Set .._log_file_size to 25 % of buffer pool size #innodb_log_file_size = 5M #innodb_log_buffer_size = 8M #innodb_flush_log_at_trx_commit = 1 #innodb_lock_wait_timeout = 50 skip-innodb [mysqldump] quick max_allowed_packet = 16M [mysql] no-auto-rehash # Remove the next comment character if you are not familiar with SQL #safe-updates [isamchk] key_buffer = 1M sort_buffer_size = 1M [myisamchk] key_buffer = 1M sort_buffer_size = 1M [mysqlhotcopy] interactive-timeout So what is my silly error?

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• In an Entity/Component system, can component data be implemented as a simple array of key-value pairs? [on hold]

  - by 010110110101

  I'm trying to wrap my head around how to organize components in an Entity Component Systems once everything in the current scene/level is loaded in memory. (I'm a hobbyist BTW) Some people seem to implement the Entity as an object that contains a list of of "Component" objects. Components contain data organized as an array of key-value pairs. Where the value is serialized "somehow". (pseudocode is loosely in C# for brevity) class Entity { Guid _id; List<Component> _components; } class Component { List<ComponentAttributeValue> _attributes; } class ComponentAttributeValue { string AttributeName; object AttributeValue; } Others describe Components as an in-memory "table". An entity acquires the component by having its key placed in a table. The attributes of the component-entity instance are like the columns in a table class Renderable_Component { List<RenderableComponentAttributeValue> _entities; } class RenderableComponentAttributeValue { Guid entityId; matrix4 transformation; // other stuff for rendering // everything is strongly typed } Others describe this actually as a table. (and such tables sound like an EAV database schema BTW) (and the value is serialized "somehow") Render_Component_Table ---------------- Entity Id Attribute Name Attribute Value and when brought into running code: class Entity { Guid _id; Dictionary<string, object> _attributes; } My specific question is: Given various components, (Renderable, Positionable, Explodeable, Hideable, etc) and given that each component has an attribute with a particular name, (TRANSLATION_MATRIX, PARTICLE_EMISSION_VELOCITY, CAN_HIDE, FAVORITE_COLOR, etc) should: an entity contain a list of components where each component, in turn, has their own array of named attributes with values serialized somehow or should components exist as in-memory tables of entity references and associated with each "row" there are "columns" representing the attribute with values that are specific to each entity instance and are strongly typed or all attributes be stored in an entity as a singular array of named attributes with values serialized somehow (could have name collisions) or something else???

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• Parallelize incremental processing in Tabular #ssas #tabular

  - by Marco Russo (SQLBI)

  I recently came in a problem trying to improve the parallelism of Tabular processing. As you know, multiple tables can be processed in parallel, whereas the processing of several partitions within the same table cannot be parallelized. When you perform an incremental update by adding only new rows to existing table, what you really do is adding rows to a partition, so adding rows to many tables means adding rows to several partitions. The particular condition you have in this case is that every partition in which you add rows belongs to a different table. Adding rows implies using the ProcessAdd command; its QueryBinding parameter specifies a SQL syntax to read new rows, otherwise the original query specified for the partition will be used, and it could generate duplicated data if you don’t have a dynamic behavior on the SQL side. If you create the required XMLA code manually, you will find that the QueryBinding node that should be part of the ProcessAdd command has to be moved out from ProcessAdd in case you are using a Batch command with more than one Process command (which is the reason why you want to use a single batch: run multiple process operations in parallel!). If you use AMO (Analysis Management Objects) you will find that this combination is not supported, even if you don’t have a syntax error compiling the code, but you might obtain this error at execution time: The syntax for the 'Process' command is incorrect. The 'Bindings' keyword cannot appear under a 'Process' command if the 'Process' command is a part of a 'Batch' command and there are more than one 'Process' commands in the 'Batch' or the 'Batch' command contains any out of line related information. In this case, the 'Bindings' keyword should be a part of the 'Batch' command only. If this is happening to you, the best solution I’ve found is manipulating the XMLA code generated by AMO moving the Binding nodes in the right place. A more detailed description of the issue and the code required to send a correct XMLA batch to Analysis Services is available in my article Parallelize ProcessAdd with AMO. By the way, the same technique (and code) can be used also if you have the same problem in a Multidimensional model.

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• "Opportunity" to take over maintenance of a small internal website. What should I do?

  - by Dan

  I have been offered an "opportunity" to take over maintenance of a small internal website run by my group that provides information about schedules and photos of events the groups done. My manager sent me the link to the site and checked it out. The site looked clean and neat but loaded in ~5 seconds. I thought this was a little long considering the site really didn't contain a lot of content. This prompted me to take a look under the hood at the pages source code. To my horror it'd been totally hacked together using nested tables! I'm new so I really can't say no to this "opportunity" so what should I do with it? Every fiber of my being feels that the only correct thing to do is over hall the site using CSS, Div's, Span's and any other appropriate tags that a sane/good web developer would used to begin with instead of depending on the render incentive magic of tables. But I'd like to ask programmers with more experienced then me, who have been in this situation. What should I do? Is my only realistic option to leave the horror as is and only adjusting the content as requested? I'm really torn between good development and the corporate reality I'm part of. Is there some kind of middle ground where things can be made better even if they're not perfect? Thanks ahead of time.

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• How can I get cross-browser consistent behavior for TR heights within a table with a set height? [migrated]

  - by Dan

  I have an arbitrary number of tables with an arbitrary number of rows in each, and all tables are the same height. My initial approach was to just set the overall height of the table and hope the rows were smart enough to distribute themselves appropriately. That's not the case. I have 4 different behaviors going on with 4 browsers, but I need them to all render at the very least in a similar way. Safari & Chrome (WebKit): All rows are equal height, creating scroll bars as needed and fitting within table height. Firefox: All rows are the height necessary to fit their content, with the remaining rows overflowing out of the table. Additionally, If the content of the rows does not take up all of the height, only the part of the table with content in it takes the background (though it seems, through use of Firebug, that the actual table [and TR] extend to the bottom of the proper table height). IE: All rows are the height necessary to fit their content, with the remaining rows overflowing out of the table. Obviously this only includes one version of each browser and additional variation would likely appear with more being tested. Ideally, a solution where the browser renders TRs with less content smaller than those with larger content, while still using scrolling within the variable height TRs when the overall height of the table is not enough would be optimum. I could potentially see a solution to achieve that with JS, but can it be done with CSS? Or, if not, can the behavior that WebKit displays be made to work across the browsers? Thanks! PS: Example can be found here.

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• First Shard for SQL Azure and SQL Server

  - by Herve Roggero

  That's it!!!!! It's ready to go and be tested, abused and improved! It requires .NET 4.0 and uses some cool technologies, like caching (the new System.Runtime.Caching) and the Task Parallel Library (System.Threading.Tasks). With this library you can: Define a shard of 1, 2 or 100 SQL databases (a mix of SQL Server and SQL Azure) Read from the shard in parallel or sequentially, and cache resultsets Update, Delete a record from the shard Insert records quickly in the shard with a round-robin load Reset the cache You can download the source code and a sample application here: http://enzosqlshard.codeplex.com/  Note about the breadcrumbs: I had to add a connection GUID in order for the library to know which database a record came from. The GUID is currently calculated on the fly in the library using some of the parameters of the connection string. The GUID is also dynamically added to the result set so the client can pass it back to the library. I am curious to get your feedback on this approach. ** Correction from my previous post: this is a library for a Horizontal Partition Shard (HPS): tables are split across databases horizontally. So in essence, the tables need to have the same schema across the databases.

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• Partitioning Strategies for P6 Reporting Database

  - by Jeffrey McDaniel

  Prior to P6 Reporting Database version 3.2 sp1 range partitioning was used. This was applied only to the history tables. The ranges were defined during installation and additional ranges would need to be added once your date range entered the final defined range. As of P6 Reporting Database version 3.2 sp1, interval partitioning was implemented. Interval partitioning was applied to the existing History table as well as Slowly Changing Dimension tables. One of the major advantages of interval partitioning is there is no more manual addition of ranges. The interval partitioning will automatically create partitions for the defined interval when data is inserted into the table and it exceeds the existing partitions. In 3.2 sp1 there are steps on how to update your partitioning. For all versions after 3.2 sp1 interval partitioning is the only partitioning option used. When upgrading it is important to be aware of these changes. Here is a link with more information on partitioning -the types and the advantages. http://docs.oracle.com/cd/E11882_01/server.112/e25523/partition.htm

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• Parameterized Django models

  - by mgibsonbr

  In principle, a single Django application can be reused in two or more projects, providing functionality relevent to both. That implies that the same database structure (tables and relations) will be re-created identically in different databases, and most times this is not a problem (assuming the projects/databases are unrelated - for instance when someone downloads a complete app to use in their own projects). Sometimes, however, the models must be "tweaked" a little to better fit the problem needs. This can be accomplished by forking the app, but I wondered if there wouldn't be a better option in cases where the app designer can anticipate the most common customizations. For instance, if I have a model that could relate to another as one-to-one or one-to-many, I could specify the unique property as a parameter, that can be specified in the project's settings: class This(models.Model): other = models.ForeignKey(Other, unique=settings.OTHER_TO_THIS) Or if a model can relate to many others, I could create an intermediate table for each of them (thus enforcing referential integrity) instead of using generic fks: for related in settings.MODELS_RELATED_TO_OTHER: model_name = '%s_Other' % related globals()[model_name] = type(model_name, (models.Model,) { me:models.ForeignKey(find_model_class(related)), other:models.ForeignKey(Other), # Some other properties all intersection tables must have }) Etc. Let me stress out that I'm not proposing to change the models at runtime nor anything like that; once the parameters were defined and syncdb called for the first time, those parameters are not to be changed again (unless you're doing a schema migration). Is this a good design? Are there better ways to accomplish the same thing, or maybe drawbacks I coulnd't anticipate? This technique is meant to be used sparingly (only on apps meant to be reused in wildly different contexts, and only when a specific need of customization can be detected while the app model is being designed).

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• What are some good tips for a developer trying to design a scalable MySQL database?

  - by CFL_Jeff

  As the question states, I am a developer, not a DBA. I have experience with designing good ER schemas and am fairly knowledgeable about normalization and good schema design. I have also worked with data warehouses that use dimensional modeling with fact tables and dim tables. However, all of the database-driven applications I've developed at previous jobs have been internal applications on the company's intranet, never receiving "real-world traffic". Furthermore, at previous jobs, I have always had a DBA or someone who knew much more than me about these things. At this new job I just started, I've been asked to develop a public-facing application with a MySQL backend and the data stored by this application is expected to grow very rapidly. Oh, and we don't have a DBA. Well, I guess I am the DBA. ;) As far as designing a database to be scalable, I don't even know where to start. Does anyone have any good tips or know of any good educational materials for a developer who has been sort of shoved into a DBA/database designer role and has been tasked with designing a scalable database to support an application like this? Have any other developers been through this sort of thing? What did you do to quickly become good at this role? I've found some good slides on the subject here but it's hard to glean details from slides. Wish I could've attended that guy's talk. I also found a good blog entry called 5 Ways to Boost MySQL Scalability which had some good information, though some of it was over my head. tl;dr I just want to make sure the database doesn't have to be completely redesigned when it scales up, and I'm looking for tips to get it right the first time. The answer I'm looking for is a "list of things every developer should know about making a scalable MySQL database so your application doesn't perform like crap when the data gets huge".

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• SQL to XML open data made simple

  - by drrwebber

  The perennial question for people is how to easily generate XML from SQL table content?  The latest CAM Editor release really tackles this head on by providing a powerful and simple toolset.  Firstly you can visually browse your SQL tables and then drag and drop from columns and tables into the XML structure editor.   This gives you a code-free method of describing the transformation you require.  So you do not need to know about the vagaries of XML and XSD schema syntax. Second you can map directly into existing industry domain XML exchange structures in the XML visual editor, again no need to wrestle with XSD schema, you have WYSIWYG visual control over what your output will look like. If you do not have a target XML structure and need to build one from scratch, then the CAM Editor makes this simple.  Switch the SQL viewer into designer mode, then take your existing SQL table and drag and drop it into the XML structure editor.  Automatically the XML wizard tool will take your SQL column names and definitions and create equivalent XML for you and insert the mappings. Simply save the structure template, and run the Open Data generator menu option, and your XML is built for you. Completely code-free template driven development. To see this in action, see our video demonstration links and then download the tools and samples and try it yourself.

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• Helping to Reduce Page Compression Failures Rate

  - by Vasil Dimov

  When InnoDB compresses a page it needs the result to fit into its predetermined compressed page size (specified with KEY_BLOCK_SIZE). When the result does not fit we call that a compression failure. In this case InnoDB needs to split up the page and try to compress again. That said, compression failures are bad for performance and should be minimized.Whether the result of the compression will fit largely depends on the data being compressed and some tables and/or indexes may contain more compressible data than others. And so it would be nice if the compression failure rate, along with other compression stats, could be monitored on a per table or even on a per index basis, wouldn't it?This is where the new INFORMATION_SCHEMA table in MySQL 5.6 kicks in. INFORMATION_SCHEMA.INNODB_CMP_PER_INDEX provides exactly this helpful information. It contains the following fields: +-----------------+--------------+------+ | Field | Type | Null | +-----------------+--------------+------+ | database_name | varchar(192) | NO | | table_name | varchar(192) | NO | | index_name | varchar(192) | NO | | compress_ops | int(11) | NO | | compress_ops_ok | int(11) | NO | | compress_time | int(11) | NO | | uncompress_ops | int(11) | NO | | uncompress_time | int(11) | NO | +-----------------+--------------+------+ similarly to INFORMATION_SCHEMA.INNODB_CMP, but this time the data is grouped by "database_name,table_name,index_name" instead of by "page_size".So a query like SELECT database_name, table_name, index_name, compress_ops - compress_ops_ok AS failures FROM information_schema.innodb_cmp_per_index ORDER BY failures DESC; would reveal the most problematic tables and indexes that have the highest compression failure rate.From there on the way to improving performance would be to try to increase the compressed page size or change the structure of the table/indexes or the data being stored and see if it will have a positive impact on performance.

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• DB Object passing between classes singleton, static or other?

  - by Stephen

  So I'm designing a reporting system at work it's my first project written OOP and I'm stuck on the design choice for the DB class. Obviously I only want to create one instance of the DB class per-session/user and then pass it to each of the classes that need it. What I don't know it what's best practice for implementing this. Currently I have code like the following:- class db { private $user = 'USER'; private $pass = 'PASS'; private $tables = array( 'user','report', 'etc...'); function __construct(){ //SET UP CONNECTION AND TABLES } }; class report{ function __construct ($params = array(), $db, $user) { //Error checking/handling trimed //$db is the database object we created $this->db = $db; //$this->user is the user object for the logged in user $this->user = $user; $this->reportCreate(); } public function setPermission($permissionId = 1) { //Note the $this->db is this the best practise solution? $this->db->permission->find($permissionId) //Note the $this->user is this the best practise solution? $this->user->checkPermission(1) $data=array(); $this->db->reportpermission->insert($data) } };//end report I've been reading about using static classes and have just come across Singletons (though these appear to be passé already?) so what's current best practice for doing this?

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• Localization of Database Strings in .Net

  - by Aligned

  I have several database tables that have a description column that I need to display in the UI. .Net has .resx files that will help with the translation of the strings, when the Thread.CurrentCulture.UICulture is set, but I needed a custom approach for the strings that are stored in the database and not in the .resx files. Here’s my approach: 1. Create a resource file for each database table and put them in the /Resources/Database/ directory. 2. Create a method in LocalizationHelpers (GetLocalizedString) that will get the string from the table for English (which should be cached to avoid unneeded service/database calls) or the resx when not English. 3. All database tables need to have a ResxKey field that matches the key in the resx file. 4. By convention the resx file will have the same name as the database table, and the key the same as the database ResxKey.   - if there are multiple columns that need translation, then one ResxKey will be used and Name or Description appended. Here’s the method I’m using to pull the string: public static string GetLocalizedString(string resourceName, string resourceKey) { if (executingAssembly == null) { executingAssembly = Assembly.GetExecutingAssembly(); } ResourceManager manager = new ResourceManager(resourceName, executingAssembly); return manager.GetString(resourceKey); }

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• MySQL December Webinars

  - by Bertrand Matthelié

  We'll be running 3 webinars next week and hope many of you will be able to join us: MySQL Replication: Simplifying Scaling and HA with GTIDs Wednesday, December 12, at 15.00 Central European TimeJoin the MySQL replication developers for a deep dive into the design and implementation of Global Transaction Identifiers (GTIDs) and how they enable users to simplify MySQL scaling and HA. GTIDs are one of the most significant new replication capabilities in MySQL 5.6, making it simple to track and compare replication progress between the master and slave servers. Register Now MySQL 5.6: Building the Next Generation of Web/Cloud/SaaS/Embedded Applications and Services Thursday, December 13, at 9.00 am Pacific Time As the world's most popular web database, MySQL has quickly become the leading cloud database, with most providers offering MySQL-based services. Indeed, built to deliver web-based applications and to scale out, MySQL's architecture and features make the database a great fit to deliver cloud-based applications. In this webinar we will focus on the improvements in MySQL 5.6 performance, scalability, and availability designed to enable DBA and developer agility in building the next generation of web-based applications. Register Now Getting the Best MySQL Performance in Your Products: Part IV, Partitioning Friday, December 14, at 9.00 am Pacific Time We're adding Partitioning to our extremely popular "Getting the Best MySQL Performance in Your Products" webinar series. Partitioning can greatly increase the performance of your queries, especially when doing full table scans over large tables. Partitioning is also an excellent way to manage very large tables. It's one of the best ways to build higher performance into your product's embedded or bundled MySQL, and particularly for hardware-constrained appliances and devices. Register Now We have live Q&A during all webinars so you'll get the opportunity to ask your questions!

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• Creating a multi-tenant application using PostgreSQL's schemas and Rails

  - by ramon.tayag

  Stuff I've already figured out I'm learning how to create a multi-tenant application in Rails that serves data from different schemas based on what domain or subdomain is used to view the application. I already have a few concerns answered: How can you get subdomain-fu to work with domains as well? Here's someone that asked the same question which leads you to this blog. What database, and how will it be structured? Here's an excellent talk by Guy Naor, and good question about PostgreSQL and schemas. I already know my schemas will all have the same structure. They will differ in the data they hold. So, how can you run migrations for all schemas? Here's an answer. Those three points cover a lot of the general stuff I need to know. However, in the next steps I seem to have many ways of implementing things. I'm hoping that there's a better, easier way. Finally, to my question When a new user signs up, I can easily create the schema. However, what would be the best and easiest way to load the structure that the rest of the schemas already have? Here are some questions/scenarios that might give you a better idea. Should I pass it on to a shell script that dumps the public schema into a temporary one, and imports it back to my main database (pretty much like what Guy Naor says in his video)? Here's a quick summary/script I got from the helpful #postgres on freenode. While this will probably work, I'm gonna have to do a lot of stuff outside of Rails, which makes me a bit uncomfortable.. which also brings me to the next question. Is there a way to do this straight from Ruby on Rails? Like create a PostgreSQL schema, then just load the Rails database schema (schema.rb - I know, it's confusing) into that PostgreSQL schema. Is there a gem/plugin that has these things already? Methods like "create_pg_schema_and_load_rails_schema(the_new_schema_name)". If there's none, I'll probably work at making one, but I'm doubtful about how well tested it'll be with all the moving parts (especially if I end up using a shell script to create and manage new PostgreSQL schemas). Thanks, and I hope that wasn't too long! UPDATE May 11, 2010 11:26 GMT+8 Since last night I've been able to get a method to work that creates a new schema and loads schema.rb into it. Not sure if what I'm doing is correct (seems to work fine, so far) but it's a step closer at least. If there's a better way please let me know. module SchemaUtils def self.add_schema_to_path(schema) conn = ActiveRecord::Base.connection conn.execute "SET search_path TO #{schema}, #{conn.schema_search_path}" end def self.reset_search_path conn = ActiveRecord::Base.connection conn.execute "SET search_path TO #{conn.schema_search_path}" end def self.create_and_migrate_schema(schema_name) conn = ActiveRecord::Base.connection schemas = conn.select_values("select * from pg_namespace where nspname != 'information_schema' AND nspname NOT LIKE 'pg%'") if schemas.include?(schema_name) tables = conn.tables Rails.logger.info "#{schema_name} exists already with these tables #{tables.inspect}" else Rails.logger.info "About to create #{schema_name}" conn.execute "create schema #{schema_name}" end # Save the old search path so we can set it back at the end of this method old_search_path = conn.schema_search_path # Tried to set the search path like in the methods above (from Guy Naor) # conn.execute "SET search_path TO #{schema_name}" # But the connection itself seems to remember the old search path. # If set this way, it works. conn.schema_search_path = schema_name # Directly from databases.rake. # In Rails 2.3.5 databases.rake can be found in railties/lib/tasks/databases.rake file = "#{Rails.root}/db/schema.rb" if File.exists?(file) Rails.logger.info "About to load the schema #{file}" load(file) else abort %{#{file} doesn't exist yet. It's possible that you just ran a migration!} end Rails.logger.info "About to set search path back to #{old_search_path}." conn.schema_search_path = old_search_path end end

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• SQL -- How to combine three SELECT statements with very tricky requirements

  - by Frederick

  I have a SQL query with three SELECT statements. A picture of the data tables generated by these three select statements is located at www.britestudent.com/pub/1.png. Each of the three data tables have identical columns. I want to combine these three tables into one table such that: (1) All rows in top table (Table1) are always included. (2) Rows in the middle table (Table2) are included only when the values in column1 (UserName) and column4 (CourseName) do not match with any row from Table1. Both columns need to match for the row in Table2 to not be included. (3) Rows in the bottom table (Table3) are included only when the value in column4 (CourseName) is not already in any row of the results from combining Table1 and Table2. I have had success in implementing (1) and (2) with an SQL query like this: SELECT DISTINCT UserName AS UserName, MAX(AmountUsed) AS AmountUsed, MAX(AnsweredCorrectly) AS AnsweredCorrectly, CourseName, MAX(course_code) AS course_code, MAX(NoOfQuestionsInCourse) AS NoOfQuestionsInCourse, MAX(NoOfQuestionSetsInCourse) AS NoOfQuestionSetsInCourse FROM ( "SELECT statement 1" UNION "SELECT statement 2" ) dt_derivedTable_1 GROUP BY CourseName, UserName Where "SELECT statement 1" is the query that generates Table1 and "SELECT statement 2" is the query that generates Table2. A picture of the data table generated by this query is located at www.britestudent.com/pub/2.png. I can get away with using the MAX() function because values in the AmountUsed and AnsweredCorrectly columns in Table1 will always be larger than those in Table2 (and they are identical in the last three columns of both tables). What I fail at is implementing (3). Any suggestions on how to do this will be appreciated. It is tricky because the UserName values in Table3 are null, and because the CourseName values in the combined Table1 and Table2 results are not unique (but they are unique in Table3). After implementing (3), the final table should look like the table in picture 2.png with the addition of the last row from Table3 (the row with the CourseName value starting with "4. Klasse..." I have tried to implement (3) using another derived table using SELECT, MAX() and UNION, but I could not get it to work. Below is my full SQL query with the lines from this failed attempt to implement (3) commented out. Cheers, Frederick PS--I am new to this forum (and new to SQL as well), but I have had more of my previous problems answered by reading other people's posts on this forum than from reading any other forum or Web site. This forum is a great resources. -- SELECT DISTINCT MAX(UserName), MAX(AmountUsed) AS AmountUsed, MAX(AnsweredCorrectly) AS AnsweredCorrectly, CourseName, MAX(course_code) AS course_code, MAX(NoOfQuestionsInCourse) AS NoOfQuestionsInCourse, MAX(NoOfQuestionSetsInCourse) AS NoOfQuestionSetsInCourse -- FROM ( SELECT DISTINCT UserName AS UserName, MAX(AmountUsed) AS AmountUsed, MAX(AnsweredCorrectly) AS AnsweredCorrectly, CourseName, MAX(course_code) AS course_code, MAX(NoOfQuestionsInCourse) AS NoOfQuestionsInCourse, MAX(NoOfQuestionSetsInCourse) AS NoOfQuestionSetsInCourse FROM ( -- Table 1 - All UserAccount/Course combinations that have had quizzez. SELECT DISTINCT dbo.win_user.user_name AS UserName, cast(dbo.GetAmountUsed(dbo.session_header.win_user_id, dbo.course.course_id, dbo.course.no_of_questionsets_in_course) as nvarchar(10)) AS AmountUsed, Isnull(cast(dbo.GetAnswerCorrectly(dbo.session_header.win_user_id, dbo.course.course_id, dbo.question_set.no_of_questions) as nvarchar(10)),0) AS AnsweredCorrectly, dbo.course.course_name AS CourseName, dbo.course.course_code, dbo.course.no_of_questions_in_course AS NoOfQuestionsInCourse, dbo.course.no_of_questionsets_in_course AS NoOfQuestionSetsInCourse FROM dbo.session_detail INNER JOIN dbo.session_header ON dbo.session_detail.session_header_id = dbo.session_header.session_header_id INNER JOIN dbo.win_user ON dbo.session_header.win_user_id = dbo.win_user.win_user_id INNER JOIN dbo.win_user_course ON dbo.win_user_course.win_user_id = dbo.win_user.win_user_id INNER JOIN dbo.question_set ON dbo.session_header.question_set_id = dbo.question_set.question_set_id RIGHT OUTER JOIN dbo.course ON dbo.win_user_course.course_id = dbo.course.course_id WHERE (dbo.session_detail.no_of_attempts = 1 OR dbo.session_detail.no_of_attempts IS NULL) AND (dbo.session_detail.is_correct = 1 OR dbo.session_detail.is_correct IS NULL) AND (dbo.win_user_course.is_active = 'True') GROUP BY dbo.win_user.user_name, dbo.course.course_name, dbo.question_set.no_of_questions, dbo.course.no_of_questions_in_course, dbo.course.no_of_questionsets_in_course, dbo.session_header.win_user_id, dbo.course.course_id, dbo.course.course_code UNION ALL -- Table 2 - All UserAccount/Course combinations that do or do not have quizzes but where the Course is selected for quizzes for that User Account. SELECT dbo.win_user.user_name AS UserName, -1 AS AmountUsed, -1 AS AnsweredCorrectly, dbo.course.course_name AS CourseName, dbo.course.course_code, dbo.course.no_of_questions_in_course AS NoOfQuestionsInCourse, dbo.course.no_of_questionsets_in_course AS NoOfQuestionSetsInCourse FROM dbo.win_user_course INNER JOIN dbo.win_user ON dbo.win_user_course.win_user_id = dbo.win_user.win_user_id RIGHT OUTER JOIN dbo.course ON dbo.win_user_course.course_id = dbo.course.course_id WHERE (dbo.win_user_course.is_active = 'True') GROUP BY dbo.win_user.user_name, dbo.course.course_name, dbo.course.no_of_questions_in_course, dbo.course.no_of_questionsets_in_course, dbo.course.course_id, dbo.course.course_code ) dt_derivedTable_1 GROUP BY CourseName, UserName -- UNION ALL -- Table 3 - All Courses. -- SELECT DISTINCT null AS UserName, -- -2 AS AmountUsed, -- -2 AS AnsweredCorrectly, -- dbo.course.course_name AS CourseName, -- dbo.course.course_code, -- dbo.course.no_of_questions_in_course AS NoOfQuestionsInCourse, -- dbo.course.no_of_questionsets_in_course AS NoOfQuestionSetsInCourse -- FROM dbo.course -- WHERE is_active = 'True' -- ) dt_derivedTable_2 -- GROUP BY CourseName -- ORDER BY CourseName

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• Can anyone help convert this VB Webservice?

  - by CraigJSte

  I can't figure it out for the life of me.. I'm using SQL DataSet Query to iterate to a Class Object which acts as a Data Model for Flex... Initially I used VB.net but now need to convert to C#.. This conversion is done except for the last section where I create a DataRow arow and then try to add the DataSet Values to the Class (Results Class)... I get an error message.. 'VTResults.Results.Ticker' is inaccessible due to its protection level (this is down at the bottom) using System; using System.Web; using System.Collections; using System.Web.Services; using System.Web.Services.Protocols; using System.Data; using System.Data.SqlClient; using System.Configuration; /// <summary> /// Summary description for VTResults /// </summary> [WebService(Namespace = "http://velocitytrading.net/ResultsVT.aspx")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class VTResults : System.Web.Services.WebService { public class Results { string Ticker; string BuyDate; decimal Buy; string SellDate; decimal Sell; string Profit; decimal Period; } [WebMethod] public Results[] GetResults() { string conn = ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString; SqlConnection myconn = new SqlConnection(conn); SqlCommand mycomm = new SqlCommand(); SqlDataAdapter myda = new SqlDataAdapter(); DataSet myds = new DataSet(); mycomm.CommandType = CommandType.StoredProcedure; mycomm.Connection = myconn; mycomm.CommandText = "dbo.Results"; myconn.Open(); myda.SelectCommand = mycomm; myda.Fill(myds); myconn.Close(); myconn.Dispose(); int i = 0; Results[] dts = new Results[myds.Tables[0].Rows.Count]; foreach(DataRow arow in myds.Tables[0].Rows) { dts[i] = new Results(); dts[i].Ticker = arow["Ticker"]; dts[i].BuyDate = arow["BuyDate"]; dts[1].Buy = arow["Buy"]; dts[i].SellDate = arow["SellDate"]; dts[i].Sell = arow["Sell"]; dts[i].Profit = arow["Profit"]; dts[i].Period = arow["Period"]; i+=1; } return dts; } } The VB.NET WEBSERVICE that runs fine which I am trying to convert to C# is here. Imports System.Web Imports System.Web.Services Imports System.Web.Services.Protocols Imports System.Data Imports System.Data.SqlClient <WebService(Namespace:="http://localhost:2597/Results/ResultsVT.aspx")> _ <WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _ <Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _ Public Class VTResults Inherits System.Web.Services.WebService Public Class Results Public Ticker As String Public BuyDate As String Public Buy As Decimal Public SellDate As String Public Sell As Decimal Public Profit As String Public Period As Decimal End Class <WebMethod()> _ Public Function GetResults() As Results() Try Dim conn As String = ConfigurationManager.ConnectionStrings("LocalSqlServer").ConnectionString Dim myconn = New SqlConnection(conn) Dim mycomm As New SqlCommand Dim myda As New SqlDataAdapter Dim myds As New DataSet mycomm.CommandType = CommandType.StoredProcedure mycomm.Connection = myconn mycomm.CommandText = "dbo.Results" myconn.Open() myda.SelectCommand = mycomm myda.Fill(myds) myconn.Close() myconn.Dispose() Dim i As Integer i = 0 Dim dts As Results() = New Results(myds.Tables(0).Rows.Count - 1) {} Dim aRow As DataRow For Each aRow In myds.Tables(0).Rows dts(i) = New Results dts(i).Ticker = aRow("Ticker") dts(i).BuyDate = aRow("BuyDate") dts(i).Buy = aRow("Buy") dts(i).SellDate = aRow("SellDate") dts(i).Sell = aRow("Sell") dts(i).Profit = aRow("Profit") dts(i).Period = aRow("Period") i += 1 Next Return dts Catch ex As DataException Throw ex End Try End Function End Class

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• Issue in Creating an Insert Query See Description Below...

  - by Parth

  I am creating a Insert Query using PHP.. By fetching the data from a Audit table and iterating the values of it in loops.. table from which I am fetching the value has the snapshot below: The Code I am using to create is given below: mysql_select_db('information_schema'); $select = mysql_query("SELECT TABLE_NAME FROM TABLES WHERE TABLE_SCHEMA = 'pranav_test'"); $selectclumn = mysql_query("SELECT * FROM COLUMNS WHERE TABLE_SCHEMA = 'pranav_test'"); mysql_select_db('pranav_test'); $seletaudit = mysql_query("SELECT * FROM jos_audittrail WHERE live = 0"); $tables = array(); $i = 0; while($row = mysql_fetch_array($select)) { $tables[$i++] =$row['TABLE_NAME']; } while($row2 = mysql_fetch_array($seletaudit)) { $audit[] =$row2; } foreach($audit as $val) { if($val['operation'] == "INSERT") { if(in_array($val['table_name'],$tables)) { $insert = "INSERT INTO '".$val['table_name']."' ("; $selfld = mysql_query("SELECT field FROM jos_audittrail WHERE table_name = '".$val['table_name']."' AND operation = 'INSERT' AND trackid = '".$val['trackid']."'"); while($row3 = mysql_fetch_array($selfld)) { $values[] = $row3; } foreach($values as $field) { $insert .= "'".$field['field']."', "; } $insert .= "]"; $insert = str_replace(", ]",")",$insert); $insert .= " values ("; $selval = mysql_query("SELECT newvalue FROM jos_audittrail WHERE table_name = '".$val['table_name']."' AND operation = 'INSERT' AND trackid = '".$val['trackid']."' AND live = 0"); while($row4 = mysql_fetch_array($selval)) { $value[] = $row4; } /*echo "<pre>"; print_r($value);exit;*/ foreach($value as $data) { $insert .= "'".$data['newvalue']."', "; } $insert .= "["; $insert = str_replace(", [",")",$insert); } } } When I Echo the $insert out of the most outer for loop (for auditrail) The values get printed as many times as the records are found for the outer for loop..i.e 'orderby= show_noauth= show_title= link_titles= show_intro= show_section= link_section= show_category= link_category= show_author= show_create_date= show_modify_date= show_item_navigation= show_readmore= show_vote= show_icons= show_pdf_icon= show_print_icon= show_email_icon= show_hits= feed_summary= page_title= show_page_title=1 pageclass_sfx= menu_image=-1 secure=0 ', '0000-00-00 00:00:00', '13', '20', '1', '152', 'accmenu', 'IPL', 'ipl', 'index.php?option=com_content&view=archive', 'component' gets repeated , i.e. INSERT INTO 'jos_menu' ('params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type') values ('orderby= show_noauth= show_title= link_titles= show_intro= show_section= link_section= show_category= link_category= show_author= show_create_date= show_modify_date= show_item_navigation= show_readmore= show_vote= show_icons= show_pdf_icon= show_print_icon= show_email_icon= show_hits= feed_summary= page_title= show_page_title=1 pageclass_sfx= menu_image=-1 secure=0 ', '0000-00-00 00:00:00', '13', '20', '1', '152', 'accmenu', 'IPL', 'ipl', 'index.php?option=com_content&view=archive', 'component', 'orderby= show_noauth= show_title= link_titles= show_intro= show_section= link_section= show_category= link_category= show_author= show_create_date= show_modify_date= show_item_navigation= show_readmore= show_vote= show_icons= show_pdf_icon= show_print_icon= show_email_icon= show_hits= feed_summary= page_title= show_page_title=1 pageclass_sfx= menu_image=-1 secure=0 ', '0000-00-00 00:00:00', '13', '20', '1', '152', 'accmenu', 'IPL', 'ipl', 'index.php?option=com_content&view=archive', 'component', 'orderby= show_noauth= .. .. .. .. and so on What I want is I should get these Values for once, I know there is mistake using the outer Forloop, but I m not getting the idea of rectifying it.. Please help... please poke me for more clarification...

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• C# Can anyone help convert this VB Webservice?

  - by CraigJSte

  I can't figure it out for the life of me.. I'm using SQL DataSet Query to iterate to a Class Object which acts as a Data Model for Flex... Initially I used VB.net but now need to convert to C#.. This conversion is done except for the last section where I create a DataRow arow and then try to add the DataSet Values to the Class (Results Class)... I get an error message.. 'VTResults.Results.Ticker' is inaccessible due to its protection level (this is down at the bottom) using System; using System.Web; using System.Collections; using System.Web.Services; using System.Web.Services.Protocols; using System.Data; using System.Data.SqlClient; using System.Configuration; /// <summary> /// Summary description for VTResults /// </summary> [WebService(Namespace = "http://velocitytrading.net/ResultsVT.aspx")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class VTResults : System.Web.Services.WebService { public class Results { string Ticker; string BuyDate; decimal Buy; string SellDate; decimal Sell; string Profit; decimal Period; } [WebMethod] public Results[] GetResults() { string conn = ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString; SqlConnection myconn = new SqlConnection(conn); SqlCommand mycomm = new SqlCommand(); SqlDataAdapter myda = new SqlDataAdapter(); DataSet myds = new DataSet(); mycomm.CommandType = CommandType.StoredProcedure; mycomm.Connection = myconn; mycomm.CommandText = "dbo.Results"; myconn.Open(); myda.SelectCommand = mycomm; myda.Fill(myds); myconn.Close(); myconn.Dispose(); int i = 0; Results[] dts = new Results[myds.Tables[0].Rows.Count]; foreach(DataRow arow in myds.Tables[0].Rows) { dts[i] = new Results(); dts[i].Ticker = arow["Ticker"]; dts[i].BuyDate = arow["BuyDate"]; dts[1].Buy = arow["Buy"]; dts[i].SellDate = arow["SellDate"]; dts[i].Sell = arow["Sell"]; dts[i].Profit = arow["Profit"]; dts[i].Period = arow["Period"]; i+=1; } return dts; } } The VB.NET WEBSERVICE that runs fine which I am trying to convert to C# is here. Imports System.Web Imports System.Web.Services Imports System.Web.Services.Protocols Imports System.Data Imports System.Data.SqlClient <WebService(Namespace:="http://localhost:2597/Results/ResultsVT.aspx")> _ <WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _ <Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _ Public Class VTResults Inherits System.Web.Services.WebService Public Class Results Public Ticker As String Public BuyDate As String Public Buy As Decimal Public SellDate As String Public Sell As Decimal Public Profit As String Public Period As Decimal End Class <WebMethod()> _ Public Function GetResults() As Results() Try Dim conn As String = ConfigurationManager.ConnectionStrings("LocalSqlServer").ConnectionString Dim myconn = New SqlConnection(conn) Dim mycomm As New SqlCommand Dim myda As New SqlDataAdapter Dim myds As New DataSet mycomm.CommandType = CommandType.StoredProcedure mycomm.Connection = myconn mycomm.CommandText = "dbo.Results" myconn.Open() myda.SelectCommand = mycomm myda.Fill(myds) myconn.Close() myconn.Dispose() Dim i As Integer i = 0 Dim dts As Results() = New Results(myds.Tables(0).Rows.Count - 1) {} Dim aRow As DataRow For Each aRow In myds.Tables(0).Rows dts(i) = New Results dts(i).Ticker = aRow("Ticker") dts(i).BuyDate = aRow("BuyDate") dts(i).Buy = aRow("Buy") dts(i).SellDate = aRow("SellDate") dts(i).Sell = aRow("Sell") dts(i).Profit = aRow("Profit") dts(i).Period = aRow("Period") i += 1 Next Return dts Catch ex As DataException Throw ex End Try End Function End Class

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• multple inner joins 3 or more crashes mysql server 5.1.30 opensolaris

  - by user331849

  when doing simple query on 4 inner joined tables, the server crashes with the output below appearing in the the mysql .err file. eg. select * from table1 inner join table2 on table1.a = table2.a and table1.b = table2.b inner join table3 on table2.a = table3.a and table2.c = table3.c inner join table4 on table3.a = table4.a and table3.d = table4.d If i remove one of the tables it executes fine. Likewise if I remove a different table, it executes fine. Though all tables have been checked anyway, this would suggest that it is not a problem specifically with one of the tables. mysql.err trace: 100503 18:13:19 - mysqld got signal 11 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=1572864000 read_buffer_size=2097152 max_used_connections=11 max_threads=151 threads_connected=10 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 2155437 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x72febda8 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = fe07efb0 thread_stack 0x40000 Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd-query at be1021f0 = explain select * from business inner join timetable on business.id = timetable.business_id inner join timetableentry on timetable.business_id = timetableentry.business_id and timetable.kid = timetableentry.parent inner join staff on timetable.business_id = staff.business_id and timetable.staf f_person = staff.kid where business.id = '3050bb04fda41df64a9c1c149150026c' thd-thread_id=9 thd-killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 100503 18:13:19 mysqld_safe mysqld restarted 100503 18:13:20 InnoDB: Failed to set DIRECTIO_ON on file ./ibdata1: OPEN: Inap propriate ioctl for device, continuing anyway 100503 18:13:20 InnoDB: Failed to set DIRECTIO_ON on file ./ibdata1: OPEN: Inap propriate ioctl for device, continuing anyway InnoDB: The log sequence number in ibdata files does not match InnoDB: the log sequence number in the ib_logfiles! 100503 18:13:20 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: Restoring possible half-written data pages from the doublewrite InnoDB: buffer... InnoDB: Last MySQL binlog file position 0 2731, file name ./mysql-bin.000093 100503 18:13:20 InnoDB: Started; log sequence number 0 2650338426 100503 18:13:20 [Note] Recovering after a crash using mysql-bin 100503 18:13:20 [Note] Starting crash recovery... 100503 18:13:20 [Note] Crash recovery finished. This on opensolaris SunOS 5.11 snv_111b i86pc i386 i86pc Mysql 5.1.30 Here is a snippet from the my.cnf file: key_buffer = 1500M max_allowed_packet = 1M thread_stack = 256K thread_cache_size = 8 sort_buffer_size = 2M read_buffer_size = 2M read_rnd_buffer_size = 8M table_cache = 512 tmp_table_size = 400M max_heap_table_size = 64M query_cache_limit = 20M query_cache_size = 200M Is this a bug or a configuration issue?

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• Survey Data Model - How to avoid EAV and excessive denormalization?

  - by AlexDPC

  Hi everyone, My database skills are mediocre at best and I have to design a data model for survey data. I have spent some thoughts on this and right now I feel that I am stuck between some kind of EAV model and a design involving hundreds of tables, each with hundreds of columns (and thousands of records). There must be a better way to do this and I hope that the wise folks on this forum can help me. I have already searched various forums, but I couldn't really find a solution. If it has already been given elsewhere, please excuse me and provide me with a link so I can read it up. Some assumptions about the data I have to deal with: Each survey consists of 1 to n questionnaires Each questionnaire consists of 100-2,000 questions (please ignore that 2,000 questions really sound like a lot to answer...) Questions can be of various types: multiple-choice, free text, a number (like age, income, percentages, ...) Each survey involves 10-200 countries (These are not the respondents. The respondents are actually people in the countries.) Depending on the type of questionnaire, each questionnaire is answered by 100-20,000 respondents per country. A country can adapt the questionnaires for a survey, i.e. add, remove or edit questions The data for one country is gathered in a separate database in that country. There is no possibility for online integration from the start. The data for all countries has to be integrated later. This means for example, if a country has deleted a question, that data must somehow be derived from what they sent in order to achieve a uniform design across all countries I will have to write the integration and cleaning software, which will need to work with every country's data In the end the data needs to be exported to flat files, one rectangular grid per country and questionnaire. I have already discussed this topic with people from various backgrounds and have not come to a good solution yet. I mainly got two kinds of opinions. The domain experts, who are used to working with flat files (spreadsheet-style) for data processing and analysis vote for a denormalized structure with loads of tables and columns as I described above (1 table per country and questionnaire). This sounds terrible to me, because I learned that wide tables are to be avoided, it will be annoying to determine which columns are actually in a table when working with it, the database will become cluttered with hundreds of tables (or I even need to set up multiple databases, each with a similar yet a bit differetn design), etc. O-O-programmers vote for a strongly "normalized" design, which would effectively lead to a central table containing all the answers from all respondents to all questions. This table would either need to contain a column of type sql_variant type or multiple answer columns with different types to store answers of different types (multiple choice, free text, ..). The former would essentially be a EAV model. I tend to follow Joe Celko here, who strongly discourages its use (he calls it OTLT or "One True Lookup Table"). The latter would imply that each row would contain null cells for the not applicable types by design. Another alternative I could think of would be to create one table per answer type, i.e., one for multiple-choice questions, one for free text questions, etc.. That's not so generic, it would lead to a lot of union joins, I think and I would have to add a table if a new answer type is invented. Sorry for boring you with all this text and thank you for your input! Cheers, Alex PS: I asked the same question here: http://www.eggheadcafe.com/community/aspnet/13/10242616/survey-data-model--how-to-avoid-eav-and-excessive-denormalization.aspx

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• How to do left joins with least-n-per-group query?

  - by Nate

  I'm trying to get a somewhat complicated query working and am not having any luck whatsoever. Suppose I have the following tables: cart_items: +--------------------------------------------+ | item_id | cart_id | movie_name | quantity | +--------------------------------------------+ | 0 | 0 | braveheart | 4 | | 1 | 0 | braveheart | 9 | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | +--------------------------------------------+ movies: +------------------------------+ | movie_id | movie_name | ... | +------------------------------+ | 0 | braveheart | . | | . | . | . | | . | . | . | | . | . | . | | . | . | . | +------------------------------+ pricing: +-----------------------------------------+ | id | movie_name | quantity | price_per | +-----------------------------------------+ | 0 | braveheart | 1 | 1.99 | | 1 | braveheart | 2 | 1.50 | | 2 | braveheart | 4 | 1.25 | | 3 | braveheart | 8 | 1.00 | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | | . | . | . | . | +-----------------------------------------+ I need to join the data from the tables, but with the added complexity that I need to get appropriate price_per from the pricing table. Only one price should be returned for each cart_item, and that should be the lowest price from the pricing table where the quantity for the cart item is at least the quantity in the pricing table. So, the query should return for each item in cart_items the following: +---------------------------------------------+ | item_id | movie_name | quantity | price_per | +---------------------------------------------+ Example 1: Variable passed to the query: cart_id = 0. Return: +---------------------------------------------+ | item_id | movie_name | quantity | price_per | +---------------------------------------------+ | 0 | braveheart | 4 | 1.25 | | 1 | braveheart | 9 | 1.00 | +---------------------------------------------+ Note that this is a minimalist example and that additional data will be pulled from the tables mentioned (particularly the movies table). How could this query be composed? I have tried using left joins and subqueries, but the difficult part is getting the price and nothing I have tried has worked. Thanks for your help. EDIT: I think this is similar to what I have working with my "real" tables: SELECT t1.item_id, t2.movie_name, t1.quantity FROM cart_items t1 LEFT JOIN movies t2 ON t2.movie_name = t1.movie_name WHERE t1.cart_id = 0 Assuming I wrote that correctly (I quickly tried to "port over" my real query), then the output would currently be: +---------------------------------+ | item_id | movie_name | quantity | +---------------------------------+ | 0 | braveheart | 4 | | 1 | braveheart | 9 | +---------------------------------+ The trouble I'm having is joining the price at a certain quantity for a movie. I simply cannot figure out how to do it.

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