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• Sybase PowerDesigner Change Many (Find/Replace/Convert) Data Item's Data Types

  - by Andy

  Hello, I have a relatively large Conceptual Data Model in PowerDesigner. After generating a Physical Data Model and seeing the DBMS data types, I need to update all of data types(NUMBER/TEXT) for each data item. I'd like to either do a find/replace within the Conceptual Data Model or somehow map to different data types when creating the Physical Data Model. Ex. Change the auto conversion of Text - Clob, to Text - NVARCHAR(20). Thanks!

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• topic for final year project

  - by Mrinal Shrivastava

  i am a computer science student and have just entered in my final year. i wanna do a project on something new and exciting in the field of networking dbms os or ai. i am proficient in java c, oracle and am improving my linux skills.. please give me some suggestions for hot topics..

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• MS SQL tuning tools for finding overload

  - by SkyFox

  I use MS SQL server as a DBMS for my very big corporate DB (with different financial data). And some times my system go down. I don't understand why. What programs/tools I can use for finding process/program/thread, that overload my SQL-server? Thanks for all answers!

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• Maximum capabilities of MySQL

  - by cdated

  How do I know when a project is just to big for MySQL and I should use something with a better reputation for scalability? Is there a max database size for MySQL before degradation of performance occurs? What factors contribute to MySQL not being a viable option compared to a commercial DBMS like Oracle or SQL Server?

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• How to backup/restore excluding filestream varbinary in SQL Server 2008?

  - by fdierre

  There is an application used in a production site that uses SQL Server 2008 as its DBMS. The database schema uses Filestream Varbinary to save binary data on the filesystem instead of directly into the DB tables. The point is that now and then it would be useful to copy the production database on development machines, mostly for doing troubleshooting. The database is too big for comfortably moving it around, but it would be ok if it could be moved leaving out the filestream varbinary fields. In other words, I am trying to make an "imperfect" copy of a database: i.e., on the destination database, it is ok to have NULL values instead of the varbinary. Is this possible? I tried looking for the feature on the SQL Server Management studio and did a backup that excludes the filegroup containing the filestream varbinary, but I cannot restore: MSSMS complains that the restore cannot be done because the backup is incomplete (of course). Is it possible to achieve what I am trying to do in some way?

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• MSSQL: Choice of service accounts

  - by Troels Arvin

  When installing MS SQL Server 2008, one needs to associate a service account with the installation (possibly even several accounts, one for the SQL Server Agent, one for Analysis Services, ..., but let's leave that for the case of simplicity). The service account may be local account, or a Windows domain account. If a domain account is used: Can MSSQL start, if connectivity to the domain controllers is temporarily down? If the answer is yes: Should each DBMS instance on each server have a separate account, or does it make sense to use a particular "MSSQL" domain account on all MSSQL-installations in the organization? If separate accounts are used for each instance on each server: Does it make sense to create a special MSSQL security group in the domain and place all the MSSQL service accounts in that group, perhaps to ease replication, etc? Is there a common, generally accepted naming convention for MSSQL service account(s)?

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• MySQL com_select?

  - by symcbean

  I'm looking to tune my query cache a bit. According to 7.6.3.4. Query Cache Status and Maintenance in the manual: The Com_select value is given by this formula: Qcache_inserts + Qcache_not_cached + queries with errors found during the column-privileges check However in 5.1.5. Server Status Variables it suggests that this is maintained by the DBMS. Having said that mysql> show status like 'Com_select%'; Always returns a value of 1 - and I'm pretty sure I've run more than one non-cached select query on my database since it started. It looks as if other people are similarly confused. Is this status variable redundant? Which bit of the manual is wrong? TIA

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• connect to my database from another computer

  - by user3482102

  Sorry for being a :noob I am a student working on a dbms project on my laptop. I have installed mariadb and I have root access. Similarly the case with my friend's laptop. The problem is we both want to work on same database collectively as we are partners of a team in the project. How can I create a database in mariadb that we both can share? How to access that database? Please specify the software to use and implementation.

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• If I use Ruby Migrations, do I have to use the rest of Ruby on Rails?

  - by jkohlhepp

  I'm currently trying to come up with a database migrations strategy for my organization. This includes getting the database scripts into source control, managing versioning, managing releases to QA / Production, managing branching and merging across different release branches, etc. Ruby Migrations seems to offer solutions to a lot of those problems. But, from looking at the Ruby on Rails docs, it is unclear to me whether Ruby Migrations can be separated from the rest of the framework. I work in a primarily .NET shop, but with a lot of other technologies, and with multiple DBMS platforms (SQL Server, Oracle of various versions). Ruby is not present in our portfolio at all right now, and we have no plans to use it. If I was to use Ruby Migrations, it would be the only piece of the Ruby on Rails framework that we would want to use. Can Ruby Migrations be effectively used to manage database changes independently of the rest of the Ruby on Rails framework? Are there any docs or articles out there that describe this workflow? (Yes, I know there are other options such as Liquibase but I'm specifically trying to learn about Ruby Migrations with this question.)

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• Is C and Python enough?

  - by gruszczy

  I am very proficient in Python (including Django), which I use for most tasks. I am also quite confident with C; I am maintaining small file system in userspace written in C. Yet when I am browsing job offers I see everywhere Java/C# and sometimes C++. I have coded profesionally in C++ for half a year in a gaming company, but I don't consider myself a pro. Also I simply despise Java and C#, which I would prefer not to touch ever. But it seems to me, that I am at very unfavorable position, when it comes to career. I am browsing careers.stackoverflow.com and I don't see and pure python or C offers. I would like to find a new job abroad in about 6 months. If I find some python offer, it means doing web development (not my favorite job). Does it mean, that I have to quickly start improving my C++ skills, if I wish to find a satisfying job? What would you suggest me? EDIT Learning new technologies is not an issue. Company I am working in is an integrator. Basically every new project requires learning new technologies, sometimes custom made. During last two years I was writing SQLs by hand, using LDAP, writing GUI in Qt, working on large scale DBMS prototype, making our internal help desk system use gsm modem or writing own report system. In previous job I had to learn from basics everything what I could about games development, because I knew nothing and chose this job only because of the challene it posed. I am all about embracing new technologies. I have used Java in the past and simply didn't like it. It's dull and boring. Doesn't let me do anything cool. I have recently seen some C# in action and seems similar. I don't like it. It's like German. I don't like speaking German.

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• How to quickly search through a very large list of strings / records on a database

  - by Giorgio

  I have the following problem: I have a database containing more than 2 million records. Each record has a string field X and I want to display a list of records for which field X contains a certain string. Each record is about 500 bytes in size. To make it more concrete: in the GUI of my application I have a text field where I can enter a string. Above the text field I have a table displaying the (first N, e.g. 100) records that match the string in the text field. When I type or delete one character in the text field, the table content must be updated on the fly. I wonder if there is an efficient way of doing this using appropriate index structures and / or caching. As explained above, I only want to display the first N items that match the query. Therefore, for N small enough, it should not be a big issue loading the matching items from the database. Besides, caching items in main memory can make retrieval faster. I think the main problem is how to find the matching items quickly, given the pattern string. Can I rely on some DBMS facilities, or do I have to build some in-memory index myself? Any ideas? EDIT I have run a first experiment. I have split the records into different text files (at most 200 records per file) and put the files in different directories (I used the content of one data field to determine the directory tree). I end up with about 50000 files in about 40000 directories. I have then run Lucene to index the files. Searching for a string with the Lucene demo program is pretty fast. Splitting and indexing took a few minutes: this is totally acceptable for me because it is a static data set that I want to query. The next step is to integrate Lucene in the main program and use the hits returned by Lucene to load the relevant records into main memory.

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• CodePlex Daily Summary for Wednesday, April 11, 2012

  CodePlex Daily Summary for Wednesday, April 11, 2012Popular ReleasesCommand-Line Database Builder: 1.0.2012.0411: Utility now supports arbitrary key:value pairs on the command-line for performing replacements in the .pp.sql files. Removed the usage of '-' to prefix key:value arguments. AspNetAssemblyPath is no longer a known key:value pair but can still be used because the tool now supports arbitrary key:value pairs for replacements. This was provided previously to support setting up ASP.NET Membership and Roles in a database. I've added a .pp.sql file to the Examples archive that demonstrates this usage.Supporting Guidance and Whitepapers: v1 - Team Foundation Service Whitepapers: Welcome to the BETA release of the Team Foundation Service Whitepapers preview As this is a BETA release and the quality bar for the final Release has not been achieved, we value your candid feedback and recommend that you do not use or deploy these BETA artifacts in a production environment. Quality-Bar Details Documentation has been reviewed by Visual Studio ALM Rangers Documentation has been through an independent technical review All critical bugs have been resolved Known Issue...Scrum Task Board Card Creator: TaskCardCreator 3.2.0.0: What's New: New report template added: Microsoft Visual Studio Scrum 1.0 Detailed Report Supported Templates: Microsoft Visual Studio Scrum 1.0 MSF for Agile Software Development v5.0Microsoft .NET Gadgeteer: .NET Gadgeteer Core 2.42.550 (BETA): Microsoft .NET Gadgeteer Core RELEASE NOTES Version 2.42.550 11 April 2012 BETA VERSION WARNING: This is a beta version! Please note: - API changes may be made before the next version (2.42.600) - The designer will not show modules/mainboards for NETMF 4.2 until you get upgraded libraries from the module/mainboard vendors - Install NETMF 4.2 (see link below) to use the new features of this release That warning aside, this version should continue to sup...DISM GUI: DISM GUI 3.1.1: Fixes - Fixed a bug in the Delete Driver function - The Index field is not auto populated with the number 1LINQ to Twitter: LINQ to Twitter Beta v2.0.24: Supports .NET 3.5, .NET 4.0, Silverlight 4.0, Windows Phone 7.1, and Client Profile. 100% Twitter API coverage. Also available via NuGet.Kendo UI ASP.NET Sample Applications: Sample Applications (2012-04-11): Sample application(s) demonstrating the use of Kendo UI in ASP.NET applications.Json.NET: Json.NET 4.5 Release 2: New feature - Added support for the SerializableAttribute and serializing a type's internal fields New feature - Added MaxDepth to JsonReader/JsonSerializer/JsonSerializerSettings New feature - Added support for ignoring properties with the NonSerializableAttribute Fix - Fixed deserializing a null string throwing a NullReferenceException Fix - Fixed JsonTextReader reading from a slow stream Fix - Fixed CultureInfo not being overridden on JsonSerializerProxy Fix - Fixed full trust ...SCCM Client Actions Tool: SCCM Client Actions Tool v1.12: SCCM Client Actions Tool v1.12 is the latest version. It comes with following changes since last version: Improved WMI date conversion to be aware of timezone differences and DST. Fixed new version check. The tool is downloadable as a ZIP file that contains four files: ClientActionsTool.hta – The tool itself. Cmdkey.exe – command line tool for managing cached credentials. This is needed for alternate credentials feature when running the HTA on Windows XP. Cmdkey.exe is natively availab...Dual Browsing: Dual Browser: Please note the following: I setup the address bar temporarily to only accepts http:// .com addresses. Just type in the name of the website excluding: http://, www., and .com; (Ex: for www.youtube.com just type: youtube then click OK). The page splitter can be grabbed by holding down your left mouse button and move left or right. By right clicking on the page background, you can choose to refresh, go back a page and so on. Demo video: http://youtu.be/L7NTFVM3JUYMultiwfn: Multiwfn 2.3.3: Multiwfn 2.3.3Liberty: v3.2.0.1 Release 9th April 2012: Change Log-Fixed -Reach Fixed a bug where the object editor did not work on non-English operating systemsPath Copy Copy: 10.1: This release addresses the following work items: 11357 11358 11359 This release is a recommended upgrade, especially for users who didn't install the 10.0.1 version.ExtAspNet: ExtAspNet v3.1.3: ExtAspNet - ?? ExtJS ??? ASP.NET 2.0 ???，????? AJAX ?????????? ExtAspNet ????? ExtJS ??? ASP.NET 2.0 ???，????? AJAX ??????????。 ExtAspNet ??????? JavaScript，?? CSS，?? UpdatePanel，?? ViewState，?? WebServices ???????。 ??????: IE 7.0, Firefox 3.6, Chrome 3.0, Opera 10.5, Safari 3.0+ ????：Apache License 2.0 (Apache) ??：http://extasp.net/ ??：http://bbs.extasp.net/ ??：http://extaspnet.codeplex.com/ ??：http://sanshi.cnblogs.com/ ????： +2012-04-08 v3.1.3 -??Language="zh_TW"?JS???BUG（??）。 +?D...Coding4Fun Tools: Coding4Fun.Phone.Toolkit v1.5.5: New Controls ChatBubble ChatBubbleTextBox OpacityToggleButton New Stuff TimeSpan languages added: RU, SK, CS Expose the physics math from TimeSpanPicker Image Stretch now on buttons Bug Fixes Layout fix so RoundToggleButton and RoundButton are exactly the same Fix for ColorPicker when set via code behind ToastPrompt bug fix with OnNavigatedTo Toast now adjusts its layout if the SIP is up Fixed some issues with Expression Blend supportHarness - Internet Explorer Automation: Harness 2.0.3: support the operation fo frameset, frame and iframe Add commands SwitchFrame GetUrl GoBack GoForward Refresh SetTimeout GetTimeout Rename commands GetActiveWindow to GetActiveBrowser SetActiveWindow to SetActiveBrowser FindWindowAll to FindBrowser NewWindow to NewBrowser GetMajorVersion to GetVersionBetter Explorer: Better Explorer 2.0.0.861 Alpha: - fixed new folder button operation not work well in some situations - removed some unnecessary code like subclassing that is not needed anymore - Added option to make Better Exlorer default (at least for WIN+E operations) - Added option to enable file operation replacements (like Terracopy) to work with Better Explorer - Added some basic usability to "Share" button - Other fixesLightFarsiDictionary - ??????? ??? ?????/???????: LightFarsiDictionary - v1: LightFarsiDictionary - v1WPF Application Framework (WAF): WPF Application Framework (WAF) 2.5.0.3: Version: 2.5.0.3 (Milestone 3): This release contains the source code of the WPF Application Framework (WAF) and the sample applications. Requirements .NET Framework 4.0 (The package contains a solution file for Visual Studio 2010) The unit test projects require Visual Studio 2010 Professional Changelog Legend: [B] Breaking change; [O] Marked member as obsolete [O] WAF: Mark the StringBuilderExtensions class as obsolete because the AppendInNewLine method can be replaced with string.Jo...ClosedXML - The easy way to OpenXML: ClosedXML 0.65.2: Aside from many bug fixes we now have Conditional Formatting The conditional formatting was sponsored by http://www.bewing.nl (big thanks) New on v0.65.1 Fixed issue when loading conditional formatting with default values for icon sets New on v0.65.2 Fixed issue loading conditional formatting Improved inserts performanceNew Projects0x10c Tools: Tools for the 0x10c-CPU: Assembler, emulator and (maybe in the future) a small compiler. Just for fun and exercise.AzureWiki: AzureWiki is the Wiki developed using Windows Azure platform which would be similar to dotnetwikiCommand-Line Database Builder: A command-line tool for interacting with a DBMS command-line interface (e.g., sqlcmd.exe) to execute a sequential list of SQL scripts against the DBMS. Tool allows for expression replacement in the SQL scripts during execution.copydata: The CopyData command-line utility enables you to easily transfer sets of data from an Oracle or SQL server data source directly to a target SQL Server database. It is developed in C#.DinoDoc: The little friendly batch-upload tool designed for SharePoint Server and Windows SharePoint Services, enabling you to easily upload multiple files and folders with a single click! For more information about DinoDoc and about SharePoint development: http://spdino.wordpress.comDiscovery House: This is a project demonstrating a green home.DocShare: DocShare illustrates the CQRS pattern on Windows Azure and also uses MVC4 Web API. DocShare uses two web roles, one for queries (reads) and one for command (writes). Each has a UI and a Web API service.EnderTecLauncher: EnderTecLauncherEntityFilter: This library provides a way to store filtering metadata, and reassemble it into dynamic lambda expressions. It allows for groups of filters to be created. Two implementations of IFilterRepository are in development:Database and XML. It's developed in C# for EntityFramework 4.1 and above.Epi Info™ - Web Analysis & Visualization: Epi Info™ is a public domain suite of software tools designed for the global community of public health practitioners and researchers. It provides for easy data entry form and database construction, a customized data entry experience, and data analyses with epidemiologic statistic Epi Info™ Web Analytics & Visualization is an open source project of the popular Epi Info™ suite of tools. The web product can be deployed as an intranet application and will provide analytical and visualization ...fOrganiz: This application allows you to automatically organize by date in specific subdirectories your picturesforwork: forworkGeneric Language - Mobile & Telephony Technologies: Genlang Mobile and Telephony Technologies, a complete application development platform for all platforms, Windows Mobile, Windows Desktop, Web, Apple, Android, BlackBerry.gindex: Graph has become increasingly important in modelling complicated structures and schemaless data such as proteins,chemical compounds, and XML documents. Given a graph query, it is desirable to retrieve graphs quickly from a large database via graph-based indices.Hijri Date SkinObject: Hijri date skin object for dotnetnuke copy to admin/skins use it in your skin file HorseRaces: Exercise inspired on example found in book "Designing for scalability with Microsoft Windows DNA" by Sten Sundblad and Per SundbladHotelMS: HotelManageSystemhtml5lmth: testjRulee: The jRulee javascript toolkit libraryKrishaTool: oloLegSec: LegSec is an small command line application for collating licence information based on that provided in Nuget packages. Modwind Domain Info: The program determines country of origin for top-level domains and purpose for international ones.MySCM Outlook Addin: This is another tool for SCM/TFS team. Use this add-in to create, update, refresh TFS work items from your Outlook emails. Not a substitution, but this little tool can help you to track your various work in TFS while educating and establishing the processes and policies.neptouni: This software can be used to convert nepali ttf text to the unicode characters.Northwind SSDT: An SSDT project for the Northwind database. This will enable you to deploy Northwind wherever you like. Note that to allow for hosting in a SQL Azure database that is used to host objects for other applications all the Northwind objects have been moved into a schema called [Northwind]Optional: Optional is a library to create options and commands from command-line arguments. It uses Convention over Configuration to get out of your way. Attributes can be used to set properties which differ from the convention.pbdevnpro1: pbdevnpro1，no1Projet LIF7 Snake: Projet LIF7 SnakePurpleStoat: A modular, extensible Silverlight application shell using Prism, Unity and the Enterprise Library, and written in C#. It includes WCF services which provide AuthZ and logging services to the shell, which are also available to the modules.Sharepoint 2010 Weather WebPart using Azure Data Market Met Office Feed: Sharepoint 2010 WebPart that displays a 5 day weather forecast for a given location. The weather data is retrieved from the Met Office feed hosted on the Windows Azure Data Market. This is a free data feed that provides weather data for the UK only.Silverlight Layouts: Silverlight Layouts is a project for controls that behave as content placeholders with pre-defined GUI layout for some of common scenarios: - frozen headers, - frozen columns, - cyrcle layouts etc.Snom Phone .NET Library: .NET Automation library for the snom IP phones. Provides simple class library to interact with you snom phone: - Press any key on the phone. - Dial numbers. - Answer or hang up call. - Mute and un-mute. - Hold and un-hold a call. - Navigate through a routing phone system using dial tone. - Get events on incoming or outgoing calls, as well as other events. - And more...Substrate Windows 8 XAML Framework: Framework for writing Windows 8 applications in XAMLTiger Converters: Tiger is a small languaje based on expressions, so it's perfect for writing the body of a WPF/SL converter.Time manager by bozheville: Time manager by bozhevilleUmbraco 501 on Windows Azure (with Dynamic Deploy): This project is configured to run Umbraco 5.0.1 on Windows Azure via the Dynamic Deploy platform. For more information on Dynamic Deploy visit http://www.dynamicdeploy.com Dynamic Deploy is a cloud deployment platform from where you can deploy applications directly to cloud platforms (like Windows Azure). UnitPrice: This is unit priceWebmedia: this is my webmedia projectWindows 8 Metro RSS Reader: A RSS Reader metro app for Windows 8 written in C# and XAML based on the sample Grid templateWindows Phone UPnP: The basics of a UPnP network stack for Windows Phone, based on a blog post originally. Written in C#, also requires the Async CTP. Includes device discovery via SSDP and method invocation.WinRT XAML Toolkit: A set of controls, extensions and helper classes for Windows Runtime XAML applicationsWmiGuru: WmiGuru is a lightweight F# library for WMI operations such as getting instances, creating instance, and querying associated instances.????: ???? ??.net mvc3??。??jquery+html5????。?????: openwebsite

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• How to ThinApp a Database Application & SQL Server 2005

  - by dandan78

  To make it easier for potential clients to try out our software without having to go to the trouble of installing SQL Server, a test database, setting up an ODBC connection and so on, we want to package the whole thing with VMWare ThinApp. Ideally, there'd be a single executable and all the user would have to do is run it. I've been reading up on ThinApp on the VMWare website but am still unsure how to go about doing this. Is the correct approach to put SQL Server and the application in separate packages, reverting to a clean version of the virtual enviroment prior to each packaging? That seems somewhat problematic because the app needs the DBMS to run, as well as an ODBC connection. Like I said, we'd prefer to go with a single package (package = executable?), but two executables are also acceptable if an alternative can't be found. I realize that the same result can probably be achieved by way of a custom SQL Server Express installation but ThinApp looks like a better and more elegant solution.

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• Studying MySQL, SQLite source code to learn about RDBMS implementation

  - by Yang

  I know implementing database is a huge topic, but I want to have a basic understanding of how database systems work (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database. Since there are a few already proven very robust open source databases like mysql, sqlite and so on. However, the code are very complicated and I have no clue where to start. Also I find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how I should get started and if there are any books that emphasis on the technology and techniques of building dbms used in modern database industry?

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• SQL Server: SELECT rows with MAX(Column A), MAX(Column B), DISTINCT by related columns

  - by z531

  Scenario: Table A MasterID, Added Date, Added By, Updated Date, Updated By, 1, 1/1/2010, 'Fred', null, null 2, 1/2/2010, 'Barney', 'Mr. Slate', 1/7/2010 3, 1/3/2010, 'Noname', null, null Table B MasterID, Added Date, Added By, Updated Date, Updated By, 1, 1/3/2010, 'Wilma', 'The Great Kazoo', 1/5/2010 2, 1/4/2010, 'Betty', 'Dino', 1/4/2010 Table C MasterID, Added Date, Added By, Updated Date, Updated By, 1, 1/5/2010, 'Pebbles', null, null 2, 1/6/2010, 'BamBam', null, null Table D MasterID, Added Date, Added By, Updated Date, Updated By, 1, 1/2/2010, 'Noname', null, null 3, 1/4/2010, 'Wilma', null, null I need to return the max added date and corresponding user, and max updated date and corresponding user for each distinct record when tables A,B,C&D are UNION'ed, i.e.: 1, 1/5/2010, 'Pebbles', 'The Great Kazoo', 1/5/2010 2, 1/6/2010, 'BamBam', 'Mr. Slate', 1/7/2010 3, 1/4/2010, 'Wilma', null, null I know how to do this with one date/user per row, but with two is beyond me. DBMS is SQL Server 2005. T-SQL solution preferred. Thanks in advance, Dave

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• how to set charset for MySQL in RODBC

  - by lokheart

  I have a data with chinese characters as field names and data, I have imported them from xls to access 2007 and export them to ODBC. Then I use RODBC to read them in R, the field names is OK, but for the data, all of the chinese characters are shown as ?. I have read the RODBC manual and it said: If it is possible to set the DBMS or ODBC driver to communicate in the character set of the R session then this should be done. For example, MySQL can set the communication character set via SQL, e.g. SET NAMES 'utf8'. I guess this is the problem, but how can I provide this command to MySQL via RODBC? Thanks!

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• mysql, sqlite database source code

  - by Yang

  hi guys, i know implementing database is a huge topic, but i want to have a basic understanding of how database systems works (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database, since there are a few already proven very robust open source databases like mysql, sqlite and so on. however, the code are very complicated and i have no clue where to start. also i find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how should i get started and is there any books that emphasis on the technology and techniques of building dbms used in modern database industry? Thank in advance!

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• Top 3 reasons not to develop a "blog system" that generates aspx files on the fly.

  - by klausbyskov

  In this question the OP implies that he wants to base the blog system he is developing on automatic creation of .aspx files, one for each new blog entry. In my answer to his question (which is related to something else), I told him that I would discourage him from using such an approach, but without giving any real reasons. He is now wanting reasons why it is not a good idea, and I'm using this question to see if the community can come up with a compelling enough list of reasons for him to use another approach, such as one using a dbms, code-reuse, url-rewriting, MVC, and what not.

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• Why would you want a case sensitive database?

  - by Khorkrak

  What are some reasons for choosing a case sensitive collation over a case insensitive one? I can see perhaps a modest performance gain for the DB engine in doing string comparisons. Is that it? If your data is set to all lower or uppercase then case sensitive could be reasonable but it's a disaster if you store mixed case data and then try to query it. You have then apply a lower() function on the column so that it'll match the corresponding lower case string literal. This prevents index usage in every dbms. So wondering why anyone would use such an option.

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• What are some best practises and "rules of thumb" for creating database indexes?

  - by Ash

  I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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• Linq to SQL EntitySet Records causing duplicate insertion

  - by Savvas Sopiadis

  In a WPF application i'm using Linq to SQL in a multi tier application. (This is an archailogy photo filing application), so every excavation has its corresponding Pictures, thus a one-to-many relationship. This relationship is correctly created by SQLMetal (which i'm using to create the POCOs). So here is the situation i 'm having trouble with: Saving changes (either of new or altered objects) is done through UnitOfWork() pattern this way: using (IUnitOfWork unitOfWork = UnitOfWork.Begin()) { //if this is a new record if (SelectedExcavation.excavation.ExcavationId == 0) { IsNewRecord = true; excavService.Add(SelectedExcavation.excavation); } //send the actual changes to the dbms unitOfWork.Commit(); } Everything works fine! BUTTTT!!! Whenever a record gets updated which has (already at least one ) corresponding Picture Record: 1) a new Excavation Record is inserted 2) the current Excavation Record gets updated 3) the previous Picture Record gets its Id changed to the newly created ExcavationId What is going on under the hood? Does Linq to SQL not handle such simple update scenarios? Thanks in advance

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• Thinking of an Inner Join as a Cross Join and then satisfying some condition(s)?

  - by Jian Lin

  It seems like the safest way to think of an Inner Join is to think of it as a Cross Join and then satisfying some condition(s)? Because the equi-join can be obvious, but the non-equi-join can be a bit confusing. But if we always use the Cross Join, and then filter out the ones satisfying the condition, then we get the resulting table. In other words, we can always analyze it by using the first record on the left table, and then go through every single records on the right, and then repeat that for 2nd record on the left, and for the 3rd, 4th, ... etc. So in our mind, we can analyze it using this way, and it is like O(n^2), although what happens in the DBMS maybe that it is a lot faster (when an index is present). Is there another good way to think of it besides this method?

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• Is it possible to have a tableless select with multiple rows?

  - by outis

  A SELECT without a FROM clause gets us a multiple columns without querying a table: SELECT 17+23, REPLACE('bannanna', 'nn', 'n'), RAND(), CURRENT_TIMESTAMP; How can we write a query that results in multiple rows without referring to a table? Basically, abuse SELECT to turn it into a data definition statement. The result could have a single column or multiple columns. I'm most interested in a DBMS neutral answer, but others (e.g. based on UNPIVOT) are welcome. There's no technique application behind this question; it's more theoretical than practical.

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• It seems like the safest way to think of an Inner Join is to think of it as a Cross Join and then sa

  - by Jian Lin

  It seems like the safest way to think of an Inner Join is to think of it as a Cross Join and then satisfying some condition(s)? Because the equi-join can be obvious, but the non-equi-join can be a bit confusing. But if we always use the Cross Join, and then filter out the ones satisfying the condition, then we get the resulting table. In other words, we can always analyze it by using the first record on the left table, and then go through every single records on the right, and then repeat that for 2nd record on the left, and for the 3rd, 4th, ... etc. So in our mind, we can analyze it using this way, and it is like O(n^2), although what happens in the DBMS maybe that it is a lot faster (when an index is present). Is there another good way to think of it besides this method?

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• Nested joins hide table names

  - by Sergio

  Hi: I have three tables: Suppliers, Parts and Types. I need to join all of them while discriminating columns with the same name (say, "id") in the three tables. I would like to successfully run this query: CREATE VIEW Everything AS SELECT Suppliers.name as supplier, Parts.id, Parts.description, Types.typedesc as type FROM Suppliers JOIN (Parts JOIN Types ON Parts.type_id = Types.id) ON Suppliers.id = Parts.supplier_id; My DBMS (sqlite) complains that "there is not such a column (Parts.id)". I guess it forgets table names once the JOIN is done but then how can I refer to the column id that belongs to the table Parts?

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