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  • Find all those columns which have only null values, in a MySQL table

    - by Robin v. G.
    The situation is as follows: I have a substantial number of tables, with each a substantial number of columns. I need to deal with this old and to-be-deprecated database for a new system, and I'm looking for a way to eliminate all columns that have - apparently - never been in use. I wanna do this by filtering out all columns that have a value on any given row, leaving me with a set of columns where the value is NULL in all rows. Of course I could manually sort every column descending, but that'd take too long as I'm dealing with loads of tables and columns. I estimate it to be 400 tables with up to 50 (!) columns per table. Is there any way I can get this information from the information_schema? EDIT: Here's an example: column_a column_b column_c column_d NULL NULL NULL 1 NULL 1 NULL 1 NULL 1 NULL NULL NULL NULL NULL NULL The output should be 'column_a' and 'column_c', for being the only columns without any filled in values.

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  • SQL CREATE TABLE Error

    - by Adam M-W
    Hi, I've been stuck on this one simple(ish) thing for the last 1/2 hour so I thought I might try to get a quick answer here. What exactly is incorrect about my SQL syntax, assuming I'm using mysql 5.1 CREATE TABLE 'users' ( 'id' MEDIUMINT(8) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, 'username' VARCHAR(20) NOT NULL, 'password' VARCHAR(40) NOT NULL, 'salt' VARCHAR(40) DEFAULT NULL, 'email' VARCHAR(80) NOT NULL, 'created_on' INT(11) UNSIGNED NOT NULL, 'last_login' INT(11) UNSIGNED DEFAULT NULL, 'active' TINYINT(1) UNSIGNED DEFAULT NULL, ) ENGINE InnoDB; Also, does anyone have any good tutorials about how to use Zend_Auth for complete noobs? Thanks.

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  • Table Adaptor Error when trying update

    - by JasonMc92
    Hi, I have a rather perplexing issue. I am using VB.net and SQL for my project. I have a database, to which the connection works. I also have a data table and data adaptor, both of which I know work. I am trying to update something in the database, yet it isn't working. Assume everything listed is declared correctly. What am I doing wrong? teacher_control_table.Rows(0)("DATA_TeacherLockPasscode") = txtPasscode1.Text table_adaptor2.Update(teacher_control_table) That last line throws the following exception: InvalidOperationException was unhandled. update requires a valid UpdateCommand when passed DataRow collection with modified rows.

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  • deleting a large number of rows from a table

    - by Azeem
    We have a requirement to delete rows in the order of millions from multiple tables as a batch job (note that we are not deleting all the rows, we are deleting based on a timestamp stored in an indexed column). Obviously a normal DELETE takes forever (because of logging, referential constraint checking etc.). I know in the LUW world, we have ALTER TABLE NOT LOGGED INITIALLY but I can't seem to find the an equivalent SQL statement for DB2 v8 z/OS. Any one has any ideas on how to do this really fast? Also, any ideas on how to avoid the referential checks when deleting the rows? Please let me know.

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  • How do I get every nth row in a table, or how do I break up a subset of a table into sets or rows of

    - by Jherico
    I have a table of heterogeneous pieces of data identified by a primary key (ID) and a type identifier (TYPE_ID). I would like to be able to perform a query that returns me a set of ranges for a given type broken into even page sizes. For instance, if there are 10,000 records of type '1' and I specify a page size of 1000, I want 10 pairs of numbers back representing values I can use in a BETWEEN clause in subsequent queries to query the DB 1000 records at a time. My initial attempt was something like this select id, rownum from CONTENT_TABLE where type_id = ? and mod(rownum, ?) = 0 But this doesn't work.

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  • read text file line by line and insert/update values in table

    - by I__
    i am exploring the option of whether DoCmd.TransferText will do what i need, and it seems like it wont. i need to insert data if it does not exist and update it if it does exist i am planning to read a text file line by line like this: Dim intFile As Integer Dim strLine As String intFile = FreeFile() Open myFile For Input As #intFile Line Input #intFile, strLine Close #intFile i guess each individual line will be a record. it will probably be comma separated and some fields will have a " text qualifier because within the field itself i will have commas my question is how would i read a comma delimited text file that has double quotes sometimes as text qualifiers into a table in access?

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  • Dtaset holds a table called "Table", not the table I pass in?

    - by dotnetdev
    Hi, I have the code below: string SQL = "select * from " + TableName; using (DS = new DataSet()) using (SqlDataAdapter adapter = new SqlDataAdapter()) using (SqlConnection sqlconn = new SqlConnection(connectionStringBuilder.ToString())) using (SqlCommand objCommand = new SqlCommand(SQL, sqlconn)) { sqlconn.Open(); adapter.SelectCommand = objCommand; adapter.Fill(DS); } System.Windows.Forms.MessageBox.Show(DS.Tables[0].TableName); return DS; However, every time I run this code, the dataset (DS) is filled with one table called "Table". It does not represent the table name I pass in as the parameter TableName and this parameter does not get mutated so I don't know where the name Table comes from. I'd expect the table to be the same as the tableName parameter I pass in? Any idea why this is not so? Thanks

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  • comparing rows on a mysql table

    - by user311324
    Ok here's the deal I got one table with a bunch of client information. Each client makes up to one purchase a year which is represented by an individual row. there's a column for the year and there's a column the contains a unique identifier for each client. What I need to do is to construct a query that takes last year and this year and shows me which clients were here made a purchase last year but not make a purchase this year. I also need to build a query that shows me which clients did not make a purchase last year and the year before last but did make a purchase this year.

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  • Creating a multi-row "table" as part of a SELECT

    - by Chad Birch
    I'm not really sure how to describe my question (thus the awful title), but it's related to this recent question. The problem would be easily solved if there was some way for me to create a "table" with 4 rows as part of my SELECT (to use with NOT IN or MINUS). What I mean is, I can do this: SELECT 1, 2, 3, 4; And will receive one row from the database: | 1 | 2 | 3 | 4 | But is there any way to receive the following (without using UNION, I don't really want a query that's potentially thousands of lines long with a long list)? | 1 | | 2 | | 3 | | 4 |

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  • stuck with creating rent table

    - by From.ME.to.YOU
    i want to create a php with mysql to do the following: lets say that i have a shop i want to rent, rent will be weekly or monthly. I'm searching for the best way to create this table, so i can do easy queries to calculate free weeks or months. EDIT let say i have ID, START_DATE,RENING_TYPE,CLIENT_ID where Start_date is the start date for renting, and RENTING_TYPE is weekly or monthly how should i run a query to know all the empty weeks or month so new clients may reserve that week/month for example a client reserve July month another client reserve the first week in June, if a new client logged in to my system and want to check all the available weeks/months, how can i achieve that ?

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  • [SQL][MS access] Query to find duplicate item in 2 table

    - by Rico
    I have this table Antecedent Consequent I1 I2 I1 I1,I2,I3 I1 I4,I1,I3,I4 I1,I2 I1 I1,I2 I1,I4 I1,I2 I1,I3 I1,I4 I3,I2 I1,I2,I3 I1,I4 I1,I3,I4 I4 AS you can see it's pretty messed up. is there anyway i can remove rows if item in consequent exist in antecedent (in 1 row) for example: INPUT: Antecedent Consequent I1 I2 I1 I1,I2,I3 <---- DELETE since I1 exist in antecedent I1 I4,I1,I3,I4 <---- DELETE since I1 exist in antecedent I1,I2 I1 <---- DELETE since I1 exist in antecedent I1,I2 I1,I4 <---- DELETE since I1 exist in antecedent I1,I2 I1,I3 <---- DELETE since I1 exist in antecedent I1,I4 I3,I2 <---- DELETE since I2 exist in antecedent I1,I2,I3 I1,I4 I1,I3,I4 I4 <---- DELETE since I4 exist in antecedent OUTPUT: Antecedent Consequent I1 I2 I1,I2,I3 I1,I4 is there anyway i can do that by query?

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  • insert into select from other table

    - by user3815079
    I need to add multiple records based on data from another table where the event is the same. I've found on this forum insert into table2(id,name) select "001",first_name from table1 where table1.id="001" as possible solution for my question. So I thought this should be the following syntax: insert into reservations(event,seat) select "99",id from seats where seats.id>0 to add all seats to event 99. However when I run this query mysql gives the message 'MySQL returned an empty resultset (0 rows). (query 0.0028 sec)' and no records were added. I translated the message so could be sligthly different. When I only use the "select "99",id from seats where seats.id0" query, it returns me 1080 rows.

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  • PathTooLongException after migrating from ASP.NET MVC 1 to ASP.NET MVC 2

    - by admax
    I had updated my app from MVC 1 to MVC 2. After that some pages throws PathTooLongException: [PathTooLongException: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters.] System.IO.Path.SafeSetStackPointerValue(Char* buffer, Int32 index, Char value) +7493057 System.IO.Path.NormalizePathFast(String path, Boolean fullCheck) +387 System.IO.Path.NormalizePath(String path, Boolean fullCheck) +36 System.IO.Path.GetFullPathInternal(String path) +21 System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath) +73 System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath) +278 System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList) +87 System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String path) +65 System.Web.InternalSecurityPermissions.PathDiscovery(String path) +29 System.Web.HttpRequest.MapPath(VirtualPath virtualPath, VirtualPath baseVirtualDir, Boolean allowCrossAppMapping) +146 System.Web.HttpRequest.MapPath(VirtualPath virtualPath) +37 System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +43 System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +28 System.Web.HttpServerUtilityWrapper.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +22 System.Web.Mvc.ViewPage.RenderView(ViewContext viewContext) +284 System.Web.Mvc.WebFormView.RenderViewPage(ViewContext context, ViewPage page) +82 System.Web.Mvc.WebFormView.Render(ViewContext viewContext, TextWriter writer) +85 System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +267 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +10 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +320 System.Web.Mvc.Controller.ExecuteCore() +104 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +36 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +7 System.Web.Mvc.<c_DisplayClass8.b_4() +34 System.Web.Mvc.Async.<c_DisplayClass1.b_0() +21 System.Web.Mvc.Async.<c__DisplayClass81.<BeginSynchronous>b__7(IAsyncResult _) +12 System.Web.Mvc.Async.WrappedAsyncResult1.End() +53 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +30 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +7 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8678910 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 I know the issue with 260-character-url-lenght in ASP.NET, but my app works fine before update to ASP.NET MVC 2.0!

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  • Linq-to-Sql IIS7 Login failed for user ‘DOMAIN\MACHINENAME$’

    - by cfdev9
    I am encountering unexpected behaviour using Linq-to-sql DataContext. When I run my application locally it works as expected however after deploying to a test server which runs IIS7, I get an error Login failed for user ‘DOMAIN\MACHINENAME$’ when attempting to open objects from the DataContext. This code explains the error, which breaks on the very last line with the error "System.Data.SqlClient.SqlException: Login failed for user". var connStr ="Data Source=server;Initial Catalog=Test;User Id=testuser;Password=password"; //Test 1 var conn1 = new System.Data.SqlClient.SqlConnection(connStr); var cmdString = "SELECT COUNT(*) FROM Table1"; var cmd = new System.Data.SqlClient.SqlCommand(cmdString, conn1); conn1.Open(); var count1 = cmd.ExecuteScalar(); conn1.Close(); //Test 2 var conn2 = new System.Data.SqlClient.SqlConnection(connStr); var context = new TestDataContext(conn2); var count2 = context.Table1s.Count(); The connection string is not even using integrated security, so why is Linq-to-sql trying to connect as a specific user? If I change the server name in the connection string I get a different error so its using atleast part of the connection string, but apparently ignoring the UserId and Password. Very confused.

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  • How to adjust size of programatically created Bitmap to match text drawn on it?

    - by TooFat
    I have the following .ashx page that takes some query string parameters and returns a bitmap with the specified text written on it. The problem I have is that I am currently just manually setting the initial size of the bitmap at 100 X 100 when what I really want is to have the bitmap be just big enough to include all the text that was written to it. How can I do this? public void ProcessRequest (HttpContext context) { context.Response.ContentType = "image/png"; string text = context.Request.QueryString["Text"]; //set FontName string fontName; if (context.Request.QueryString["FontName"] != null) { fontName = context.Request.QueryString["FontName"]; } else { fontName = "Arial"; } //Set FontSize int fontEms; if (context.Request.QueryString["FontSize"] != null) { string fontSize = context.Request.QueryString["FontSize"]; fontEms = Int32.Parse(fontSize); } else { fontEms = 12; } //Set Font Color System.Drawing.Color color; if (context.Request.QueryString["FontColor"] != null) { string fontColor = context.Request.QueryString["FontColor"]; color = System.Drawing.ColorTranslator.FromHtml(fontColor); context.Response.Write(color.ToString()); } else { color = System.Drawing.Color.Red; } using (System.Drawing.Text.PrivateFontCollection fnts = new System.Drawing.Text.PrivateFontCollection()) using (System.Drawing.FontFamily fntfam = new System.Drawing.FontFamily(fontName)) using (System.Drawing.SolidBrush brush = new System.Drawing.SolidBrush(color)) using (System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(100, 100)) { using (System.Drawing.Font fnt = new System.Drawing.Font(fntfam, fontEms)) { fnts.AddFontFile(System.IO.Path.Combine(@"C:\Development\Fonts\", fontName)); System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(bmp); graph.DrawString(text, fnt, brush, new System.Drawing.Point(0, 0)); string imgPath = System.IO.Path.Combine(@"C:\Development\MyPath\Images\Text", System.IO.Path.GetRandomFileName()); bmp.Save(imgPath); context.Response.WriteFile(imgPath); } } }

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  • Employee Info Starter Kit - Visual Studio 2010 and .NET 4.0 Version (4.0.0) Available

    - by joycsharp
    Employee Info Starter Kit is a ASP.NET based web application, which includes very simple user requirements, where we can create, read, update and delete (crud) the employee info of a company. Based on just a database table, it explores and solves all major problems in web development architectural space.  This open source starter kit extensively uses major features available in latest Visual Studio, ASP.NET and Sql Server to make robust, scalable, secured and maintanable web applications quickly and easily. Since it's first release, this starter kit achieved a huge popularity in web developer community and includes 1,40,000+ download from project web site. Visual Studio 2010 and .NET 4.0 came up with lots of exciting features to make software developers life easier.  A new version (v4.0.0) of Employee Info Starter Kit is now available in both MSDN Code Gallery and CodePlex. Chckout the latest version of this starter kit to enjoy cool features available in Visual Studio 2010 and .NET 4.0. [ Release Notes ] Architectural Overview Simple 2 layer architecture (user interface and data access layer) with 1 optional cache layer ASP.NET Web Form based user interface Custom Entity Data Container implemented (with primitive C# types for data fields) Active Record Design Pattern based Data Access Layer, implemented in C# and Entity Framework 4.0 Sql Server Stored Procedure to perform actual CRUD operation Standard infrastructure (architecture, helper utility) for automated integration (bottom up manner) and unit testing Technology UtilizedProgramming Languages/Scripts Browser side: JavaScript Web server side: C# 4.0 Database server side: T-SQL .NET Framework Components .NET 4.0 Entity Framework .NET 4.0 Optional/Named Parameters .NET 4.0 Tuple .NET 3.0+ Extension Method .NET 3.0+ Lambda Expressions .NET 3.0+ Aanonymous Type .NET 3.0+ Query Expressions .NET 3.0+ Automatically Implemented Properties .NET 3.0+ LINQ .NET 2.0 + Partial Classes .NET 2.0 + Generic Type .NET 2.0 + Nullable Type   ASP.NET 3.5+ List View (TBD) ASP.NET 3.5+ Data Pager (TBD) ASP.NET 2.0+ Grid View ASP.NET 2.0+ Form View ASP.NET 2.0+ Skin ASP.NET 2.0+ Theme ASP.NET 2.0+ Master Page ASP.NET 2.0+ Object Data Source ASP.NET 1.0+ Role Based Security Visual Studio Features Visual Studio 2010 CodedUI Test Visual Studio 2010 Layer Diagram Visual Studio 2010 Sequence Diagram Visual Studio 2010 Directed Graph Visual Studio 2005+ Database Unit Test Visual Studio 2005+ Unit Test Visual Studio 2005+ Web Test Visual Studio 2005+ Load Test Sql Server Features Sql Server 2005 Stored Procedure Sql Server 2005 Xml type Sql Server 2005 Paging support

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  • Uninstalling Reporting Server 2008 on Windows Server 2008

    - by Piotr Rodak
    Ha. I had quite disputable pleasure of installing and reinstalling and reinstalling and reinstalling – I think about 5 times before it worked – Reporting Server 2008 on Windows Server with the same year number in name. During my struggle I came across an error which seems to be not quite unfamiliar to some more unfortunate developers and admins who happen to uninstall SSRS 2008 from the server. I had the SSRS 2008 installed as named instance, SQL2008. I wanted to uninstall the server and install it to default instance. And this is when it bit me – not the first time and not the last that day . The setup complained that it couldn’t access a DLL: Error message: TITLE: Microsoft SQL Server 2008 Setup ------------------------------ The following error has occurred: Access to the path 'C:\Windows\SysWOW64\perf-ReportServer$SQL2008-rsctr.dll' is denied. For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft+SQL+Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=10.0.1600.22&EvtType=0x60797DC7%25400x84E8D3C0 ------------------------------ BUTTONS: OK This is a screenshot that shows the above error: This issue seems to have a bit of literature dedicated to it and even seemingly a KB article http://support.microsoft.com/kb/956173 and a similar Connect item: http://connect.microsoft.com/SQLServer/feedback/details/363653/error-messages-when-upgrading-from-sql-2008-rc0-to-rtm The article describes issue as following: When you try to uninstall Microsoft SQL Server 2008 Reporting Services from the server, you may receive the following error message: An error has occurred: Access to the path 'Drive_Letter:\WINDOWS\system32\perf-ReportServer-rsctr.dll' is denied. Note Drive_Letter refers to the disc drive into which the SQL Server installation media is inserted. In my case, the Note was not true; the error pointed to a dll that was located in Windows folder on C:\, not where the installation media were. Despite this difference I tried to identify any processes that might be keeping lock on the dll. I downloaded Sysinternals process explorer and ran it to find any processes I could stop. Unfortunately, there was no such process. I tried to rerun the installation, but it failed at the same step. Eventually I decided to remove the dll before the setup was executed. I changed name of the dll to be able to restore it in case of some issues. Interestingly, Windows let me do it, which means that indeed, it was not locked by any process. I ran the setup and this time it uninstalled the instance without any problems:   To summarize my experience I should say – be very careful, don’t leave any leftovers after uninstallation – remove/rename any folders that are left after setup has finished. For some reason, setup doesn’t remove folders and certain files. Installation on Windows Server 2008 requires more attention than on Windows 2003 because of the changed security model, some actions can be executed only by administrator in elevated execution mode. In general, you have to get used to UAC and a bit different experience than with Windows Server 2003. Technorati Tags: SQL Server 2008,Windows Server 2008,SRS,Reporting Services

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5 Part 1: Table per Hierarchy (TPH)

    - by mortezam
    A simple strategy for mapping classes to database tables might be “one table for every entity persistent class.” This approach sounds simple enough and, indeed, works well until we encounter inheritance. Inheritance is such a visible structural mismatch between the object-oriented and relational worlds because object-oriented systems model both “is a” and “has a” relationships. SQL-based models provide only "has a" relationships between entities; SQL database management systems don’t support type inheritance—and even when it’s available, it’s usually proprietary or incomplete. There are three different approaches to representing an inheritance hierarchy: Table per Hierarchy (TPH): Enable polymorphism by denormalizing the SQL schema, and utilize a type discriminator column that holds type information. Table per Type (TPT): Represent "is a" (inheritance) relationships as "has a" (foreign key) relationships. Table per Concrete class (TPC): Discard polymorphism and inheritance relationships completely from the SQL schema.I will explain each of these strategies in a series of posts and this one is dedicated to TPH. In this series we'll deeply dig into each of these strategies and will learn about "why" to choose them as well as "how" to implement them. Hopefully it will give you a better idea about which strategy to choose in a particular scenario. Inheritance Mapping with Entity Framework Code FirstAll of the inheritance mapping strategies that we discuss in this series will be implemented by EF Code First CTP5. The CTP5 build of the new EF Code First library has been released by ADO.NET team earlier this month. EF Code-First enables a pretty powerful code-centric development workflow for working with data. I’m a big fan of the EF Code First approach, and I’m pretty excited about a lot of productivity and power that it brings. When it comes to inheritance mapping, not only Code First fully supports all the strategies but also gives you ultimate flexibility to work with domain models that involves inheritance. The fluent API for inheritance mapping in CTP5 has been improved a lot and now it's more intuitive and concise in compare to CTP4. A Note For Those Who Follow Other Entity Framework ApproachesIf you are following EF's "Database First" or "Model First" approaches, I still recommend to read this series since although the implementation is Code First specific but the explanations around each of the strategies is perfectly applied to all approaches be it Code First or others. A Note For Those Who are New to Entity Framework and Code-FirstIf you choose to learn EF you've chosen well. If you choose to learn EF with Code First you've done even better. To get started, you can find a great walkthrough by Scott Guthrie here and another one by ADO.NET team here. In this post, I assume you already setup your machine to do Code First development and also that you are familiar with Code First fundamentals and basic concepts. You might also want to check out my other posts on EF Code First like Complex Types and Shared Primary Key Associations. A Top Down Development ScenarioThese posts take a top-down approach; it assumes that you’re starting with a domain model and trying to derive a new SQL schema. Therefore, we start with an existing domain model, implement it in C# and then let Code First create the database schema for us. However, the mapping strategies described are just as relevant if you’re working bottom up, starting with existing database tables. I’ll show some tricks along the way that help you dealing with nonperfect table layouts. Let’s start with the mapping of entity inheritance. -- The Domain ModelIn our domain model, we have a BillingDetail base class which is abstract (note the italic font on the UML class diagram below). We do allow various billing types and represent them as subclasses of BillingDetail class. As for now, we support CreditCard and BankAccount: Implement the Object Model with Code First As always, we start with the POCO classes. Note that in our DbContext, I only define one DbSet for the base class which is BillingDetail. Code First will find the other classes in the hierarchy based on Reachability Convention. public abstract class BillingDetail  {     public int BillingDetailId { get; set; }     public string Owner { get; set; }             public string Number { get; set; } } public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } } public class CreditCard : BillingDetail {     public int CardType { get; set; }                     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } } public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; } } This object model is all that is needed to enable inheritance with Code First. If you put this in your application you would be able to immediately start working with the database and do CRUD operations. Before going into details about how EF Code First maps this object model to the database, we need to learn about one of the core concepts of inheritance mapping: polymorphic and non-polymorphic queries. Polymorphic Queries LINQ to Entities and EntitySQL, as object-oriented query languages, both support polymorphic queries—that is, queries for instances of a class and all instances of its subclasses, respectively. For example, consider the following query: IQueryable<BillingDetail> linqQuery = from b in context.BillingDetails select b; List<BillingDetail> billingDetails = linqQuery.ToList(); Or the same query in EntitySQL: string eSqlQuery = @"SELECT VAlUE b FROM BillingDetails AS b"; ObjectQuery<BillingDetail> objectQuery = ((IObjectContextAdapter)context).ObjectContext                                                                          .CreateQuery<BillingDetail>(eSqlQuery); List<BillingDetail> billingDetails = objectQuery.ToList(); linqQuery and eSqlQuery are both polymorphic and return a list of objects of the type BillingDetail, which is an abstract class but the actual concrete objects in the list are of the subtypes of BillingDetail: CreditCard and BankAccount. Non-polymorphic QueriesAll LINQ to Entities and EntitySQL queries are polymorphic which return not only instances of the specific entity class to which it refers, but all subclasses of that class as well. On the other hand, Non-polymorphic queries are queries whose polymorphism is restricted and only returns instances of a particular subclass. In LINQ to Entities, this can be specified by using OfType<T>() Method. For example, the following query returns only instances of BankAccount: IQueryable<BankAccount> query = from b in context.BillingDetails.OfType<BankAccount>() select b; EntitySQL has OFTYPE operator that does the same thing: string eSqlQuery = @"SELECT VAlUE b FROM OFTYPE(BillingDetails, Model.BankAccount) AS b"; In fact, the above query with OFTYPE operator is a short form of the following query expression that uses TREAT and IS OF operators: string eSqlQuery = @"SELECT VAlUE TREAT(b as Model.BankAccount)                       FROM BillingDetails AS b                       WHERE b IS OF(Model.BankAccount)"; (Note that in the above query, Model.BankAccount is the fully qualified name for BankAccount class. You need to change "Model" with your own namespace name.) Table per Class Hierarchy (TPH)An entire class hierarchy can be mapped to a single table. This table includes columns for all properties of all classes in the hierarchy. The concrete subclass represented by a particular row is identified by the value of a type discriminator column. You don’t have to do anything special in Code First to enable TPH. It's the default inheritance mapping strategy: This mapping strategy is a winner in terms of both performance and simplicity. It’s the best-performing way to represent polymorphism—both polymorphic and nonpolymorphic queries perform well—and it’s even easy to implement by hand. Ad-hoc reporting is possible without complex joins or unions. Schema evolution is straightforward. Discriminator Column As you can see in the DB schema above, Code First has to add a special column to distinguish between persistent classes: the discriminator. This isn’t a property of the persistent class in our object model; it’s used internally by EF Code First. By default, the column name is "Discriminator", and its type is string. The values defaults to the persistent class names —in this case, “BankAccount” or “CreditCard”. EF Code First automatically sets and retrieves the discriminator values. TPH Requires Properties in SubClasses to be Nullable in the Database TPH has one major problem: Columns for properties declared by subclasses will be nullable in the database. For example, Code First created an (INT, NULL) column to map CardType property in CreditCard class. However, in a typical mapping scenario, Code First always creates an (INT, NOT NULL) column in the database for an int property in persistent class. But in this case, since BankAccount instance won’t have a CardType property, the CardType field must be NULL for that row so Code First creates an (INT, NULL) instead. If your subclasses each define several non-nullable properties, the loss of NOT NULL constraints may be a serious problem from the point of view of data integrity. TPH Violates the Third Normal FormAnother important issue is normalization. We’ve created functional dependencies between nonkey columns, violating the third normal form. Basically, the value of Discriminator column determines the corresponding values of the columns that belong to the subclasses (e.g. BankName) but Discriminator is not part of the primary key for the table. As always, denormalization for performance can be misleading, because it sacrifices long-term stability, maintainability, and the integrity of data for immediate gains that may be also achieved by proper optimization of the SQL execution plans (in other words, ask your DBA). Generated SQL QueryLet's take a look at the SQL statements that EF Code First sends to the database when we write queries in LINQ to Entities or EntitySQL. For example, the polymorphic query for BillingDetails that you saw, generates the following SQL statement: SELECT  [Extent1].[Discriminator] AS [Discriminator],  [Extent1].[BillingDetailId] AS [BillingDetailId],  [Extent1].[Owner] AS [Owner],  [Extent1].[Number] AS [Number],  [Extent1].[BankName] AS [BankName],  [Extent1].[Swift] AS [Swift],  [Extent1].[CardType] AS [CardType],  [Extent1].[ExpiryMonth] AS [ExpiryMonth],  [Extent1].[ExpiryYear] AS [ExpiryYear] FROM [dbo].[BillingDetails] AS [Extent1] WHERE [Extent1].[Discriminator] IN ('BankAccount','CreditCard') Or the non-polymorphic query for the BankAccount subclass generates this SQL statement: SELECT  [Extent1].[BillingDetailId] AS [BillingDetailId],  [Extent1].[Owner] AS [Owner],  [Extent1].[Number] AS [Number],  [Extent1].[BankName] AS [BankName],  [Extent1].[Swift] AS [Swift] FROM [dbo].[BillingDetails] AS [Extent1] WHERE [Extent1].[Discriminator] = 'BankAccount' Note how Code First adds a restriction on the discriminator column and also how it only selects those columns that belong to BankAccount entity. Change Discriminator Column Data Type and Values With Fluent API Sometimes, especially in legacy schemas, you need to override the conventions for the discriminator column so that Code First can work with the schema. The following fluent API code will change the discriminator column name to "BillingDetailType" and the values to "BA" and "CC" for BankAccount and CreditCard respectively: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) {     modelBuilder.Entity<BillingDetail>()                 .Map<BankAccount>(m => m.Requires("BillingDetailType").HasValue("BA"))                 .Map<CreditCard>(m => m.Requires("BillingDetailType").HasValue("CC")); } Also, changing the data type of discriminator column is interesting. In the above code, we passed strings to HasValue method but this method has been defined to accepts a type of object: public void HasValue(object value); Therefore, if for example we pass a value of type int to it then Code First not only use our desired values (i.e. 1 & 2) in the discriminator column but also changes the column type to be (INT, NOT NULL): modelBuilder.Entity<BillingDetail>()             .Map<BankAccount>(m => m.Requires("BillingDetailType").HasValue(1))             .Map<CreditCard>(m => m.Requires("BillingDetailType").HasValue(2)); SummaryIn this post we learned about Table per Hierarchy as the default mapping strategy in Code First. The disadvantages of the TPH strategy may be too serious for your design—after all, denormalized schemas can become a major burden in the long run. Your DBA may not like it at all. In the next post, we will learn about Table per Type (TPT) strategy that doesn’t expose you to this problem. References ADO.NET team blog Java Persistence with Hibernate book a { text-decoration: none; } a:visited { color: Blue; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } p.MsoNormal { margin-top: 0in; margin-right: 0in; margin-bottom: 10.0pt; margin-left: 0in; line-height: 115%; font-size: 11.0pt; font-family: "Calibri" , "sans-serif"; }

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  • float right image pushes down text in table below in IE9 [migrated]

    - by Cheers and hth. - Alf
    I'm not a webmaster, not even a web developer, but I'm tasked with adding content to a Wordpress site developed by Someone Else(TM). Here's a page illustrating the problem: http://www.reginedagan.no/program/fiskekonkurranse-i-hovden/. It shows up nice in Firefox: But in IE9 the floated picture pushed down the text in the table below, so that it looks rather awful: I found some related questions on the web, e.g. "CSS: Float right in IE doesn't work!" and "why does a floating DIV mess up table positioning?", and the suggestions there led me to set clear: none on the div around the table, the table itself, and then each individual tr and finally even on each individual td. I also set width="99%" on the table, and tried (but I don't know how correctly) to apply the IE6 quirk fix margin-right: -3px. So here's the content as written in Wordpress, including the unsuccessful attempted fixes: <h1><div style="float: right"><a href="http://www.reginedagan.no/?attachment_id=671"><img src="http://www.reginedagan.no/wp-content/uploads/2012/06/fiskekonkurranse-2011-bilde-3-nedskalert.jpg" alt="Fra fiskekonkurransen i 2011" title="Fra fiskekonkurransen i 2011" width="200" height="242" class="size-full wp-image-671"/></a></div>Fiskekonkurranse i Hovden!</h1> <div style="background-color: #FAF0F0; clear: none;"><table width="99%" style="clear: none; right-margin: -3px;"> <tr style=" clear: none;"> <td style="text-align: left; clear: none;">Dato:</td> <td style="text-align: left; clear: none;">Lørdag 21.juli</td> </tr> <tr style=" clear: none;"> <td style="text-align: left; padding-left: 2em"; clear: none;>/ barn, Flytebrygga</td> <td style="text-align: left; clear: none;">15.00 &ndash; 16.00</td> </tr> <tr style=" clear: none;"> <td style="text-align: left; padding-left: 2em; clear: none;">/ voksne (over 12 år), Moloen</td> <td style="text-align: left; clear: none;">15.00 &ndash; 17.00 </td> </tr> <tr style=" clear: none;"> <td style="text-align: left; clear: none;">Sted:</td> <td style="text-align: left; clear: none;">Hovden</td> </tr> <tr style=" clear: none;"> <td style="text-align: left; clear: none;">Pris:</td> <td style="text-align: left; clear: none;">voksen (over 12 år) kr. 50,-, barn kr. 30,-</td> </tr style=" clear: none;"> <tr> <td style="text-align: left; clear: none;">Arrangør:</td> <td style="text-align: left; clear: none;">Hovden Grendelag</td> </tr> </table></div> Velkommen til den årlige Fiskekonkurransen i Hovden lørdag 21. juli! <a href="http://www.reginedagan.no/program/fiskekonkurranse-i-hovden/fiskekonkurranse-2011-bilde-nedskalertjpg/" rel="attachment wp-att-672"><img src="http://www.reginedagan.no/wp-content/uploads/2012/03/fiskekonkurranse-2011-bilde-nedskalertjpg.jpg" alt="Fra fiskekonkurransen i 2011" title="Fra fiskekonkurransen i 2011" width="400" height="267" class="alignleft size-full wp-image-672" /></a>Det blir stangfiske fra moloen og egen barnekonkurranse fra flytebrygga. Premiering for størst fisk, størst antall kg og flest antall stk. Premiering for barn kl. 16:30 på moloen. Alle premieres. Premiering for voksne på festen om kvelden. Salg av pølser og brus, vafler og kaffe, samt sluker. <div style="clear: left; border: 1px dashed gray; padding: 1em;"> Fest på Hovden samfunnshus kl. 21 &ndash; 02. Musikk: «Mister West», Steinar Aarsnes, Andøya. CC. Salg av øl/vin og snacks. </div> VEL MØTT &mdash; SKITT FISKE! And the resulting HTML served to a browser (only the relevant first part): <div style="float: right;"><a href="http://www.reginedagan.no/?attachment_id=671"><img src="http://www.reginedagan.no/wp-content/uploads/2012/06/fiskekonkurranse-2011-bilde-3-nedskalert.jpg" alt="Fra fiskekonkurransen i 2011" title="Fra fiskekonkurransen i 2011" class="size-full wp-image-671" height="242" width="200"></a></div> <p>Fiskekonkurranse i Hovden!</p></h1> <div style="background-color: rgb(250, 240, 240); clear: none;"> <table style="clear: none;" width="99%"> <tbody><tr style="clear: none;"> <td style="text-align: left; clear: none;">Dato:</td> <td style="text-align: left; clear: none;">Lørdag 21.juli</td> </tr> The able to reproduce the effect with simpler code by setting clear: right on the table. However, I'm unable to reproduce the effect with default styling or with clear: none (as above). So it seems maybe it's something Wordpress does, or maybe it's something the theme thing or whatever it is does – but it's very similar to what others have observed, so there is strong indication that it's also a quirk in IE. Help?

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  • Hekaton – SQL Server’s in-memory database engine

    - by Christian
    Microsoft have just gone public at the PASS Summit in Seattle about a new SQL Server engine that they’re working on which is optimized for high-memory servers – an in-memory OLTP database engine which is built-in to SQL Server rather than a separate entity.  This means that you can move just the performance critical parts of your database to Hekaton. The new engine really pushes the performance boundaries by eliminating as many instructions as possible: Main memory optimized tables which are decoupled from on-disk structures; Everything is lock and latch free; More work is pushed to compile time so your T-SQL code is compiled natively into low-level code. We’re already working with a customer on an early adoption program so expect to hear from us on what we learn about implementing it!   Christian Bolton - MCA, MCM, MVP Technical Director http://coeo.com - SQL Server Consulting & Managed Services

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  • Data Quality and Master Data Management Resources

    - by Dejan Sarka
    Many companies or organizations do regular data cleansing. When you cleanse the data, the data quality goes up to some higher level. The data quality level is determined by the amount of work invested in the cleansing. As time passes, the data quality deteriorates, and you need to repeat the cleansing process. If you spend an equal amount of effort as you did with the previous cleansing, you can expect the same level of data quality as you had after the previous cleansing. And then the data quality deteriorates over time again, and the cleansing process starts over and over again. The idea of Data Quality Services is to mitigate the cleansing process. While the amount of time you need to spend on cleansing decreases, you will achieve higher and higher levels of data quality. While cleansing, you learn what types of errors to expect, discover error patterns, find domains of correct values, etc. You don’t throw away this knowledge. You store it and use it to find and correct the same issues automatically during your next cleansing process. The following figure shows this graphically. The idea of master data management, which you can perform with Master Data Services (MDS), is to prevent data quality from deteriorating. Once you reach a particular quality level, the MDS application—together with the defined policies, people, and master data management processes—allow you to maintain this level permanently. This idea is shown in the following picture. OK, now you know what DQS and MDS are about. You can imagine the importance on maintaining the data quality. Here are some resources that help you preparing and executing the data quality (DQ) and master data management (MDM) activities. Books Dejan Sarka and Davide Mauri: Data Quality and Master Data Management with Microsoft SQL Server 2008 R2 – a general introduction to MDM, MDS, and data profiling. Matching explained in depth. Dejan Sarka, Matija Lah and Grega Jerkic: MCTS Self-Paced Training Kit (Exam 70-463): Building Data Warehouses with Microsoft SQL Server 2012 – I wrote quite a few chapters about DQ and MDM, and introduced also SQL Server 2012 DQS. Thomas Redman: Data Quality: The Field Guide – you should start with this book. Thomas Redman is the father of DQ and MDM. Tyler Graham: Microsoft SQL Server 2012 Master Data Services – MDS in depth from a product team mate. Arkady Maydanchik: Data Quality Assessment – data profiling in depth. Tamraparni Dasu, Theodore Johnson: Exploratory Data Mining and Data Cleaning – advanced data profiling with data mining. Forthcoming presentations I am presenting a DQS and MDM seminar at PASS SQL Rally Amsterdam 2013: Wednesday, November 6th, 2013: Enterprise Information Management with SQL Server 2012 – a good kick start to your first DQ and / or MDM project. Courses Data Quality and Master Data Management with SQL Server 2012 – I wrote a 2-day course for SolidQ. If you are interested in this course, which I could also deliver in a shorter seminar way, you can contact your closes SolidQ subsidiary, or, of course, me directly on addresses [email protected] or [email protected]. This course could also complement the existing courseware portfolio of training providers, which are welcome to contact me as well. Start improving the quality of your data now!

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  • Tuesday 6th Manchester SQL User Group - Chris Testa-O'Neil (Loading a datawarehouse using SSIS) and

    - by tonyrogerson
    Chris will give a talk on Loading a datawarehouse using SQL Server Integration Services, Tony Rogerson will give a talk on Database Design: Normalisation/Denormalisation and using Surrogate Keys - practicalities/pitfalls and benefits in Microsoft SQL Server. Registration is essential which you can do here: http://sqlserverfaq.com?eid=218 . Come and join us for an evening of SQL Server discussion, as well as the two formal sessions by Chris Testa-O'Neil and Tony Rogerson there will be a chance...(read more)

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  • Making Money from your SQL Server Blog

    - by Bill Graziano
    My SQL Server blog reading list is around one hundred blogs.  Many people are writing great content and generating lots of page views.  I see some of them running Google AdSense and trying to make a little money off their traffic.  If you want to earn some some extra money from what you’ve written there are a couple of options.  And one new option that I’m announcing here. Background Internet advertising is sold based on a few different pricing schemes.  Flat Fee.  You offer either all your impressions (page views) or some percentage of your impressions in exchange for a flat monthly fee.  CPM or cost per thousand impressions.  If the quoted price is $2 CPM you’ll get $2 for every 1,000 times the ad is displayed.  While you might think the “M” means millions, the “M” in CPM is the roman numeral for 1,000. CPC or cost per click.  This is also called PPC or pay per click.  In this method you get paid based on how many clicks there are on the ad.  CPA or cost per action.  In this method you get paid based on an action that occurs on the advertisers site after they click on the ad.  This is typically some type of sign up form.  This is how most affiliate programs work. Darren Rowse at ProBlogger has been writing about blogging and making money off blogs for years.  He has a good introduction to making money on your blog in his “Making Money” section.  If you’re interested in learning more he has a post up titled How to Make More Money From Your Blog in the New Year that links to many of his best posts on the subject. Google AdSense This is the most common method for people earning money from their blogging.  It’s easy to setup and administer.  You tell AdSense what size ads you’d like to run and it gives you a little piece of JavaScript to put on your site.  AdSense quickly learns the topics you write about and displays ads that are appropriate for your site.  I typically see ads for hosting, SQL Server tools and developer tools running in AdSense slots.  AdSense pays on a CPC model.  If you translate that back to CPM pricing you’ll see rates from $0.50 to $1.00 CPM. Amazon While you might not make much money writing books it’s now possible to make even less helping Amazon sell them.  You can sign up for an Amazon affiliate program.  Each time you send Amazon a link and someone buys the book you get a cut of that sale.  This is the CPA model from above.  Amazon can help you build some pretty nice “stores”.  Here’s the SQL Server bookstore I built for SQLTeam.com.  If you’re just putting in a page with books like I’ve done on SQLTeam you should keep your expectations low.  If you’re writing book reviews of suggesting books on your blog it really does make sense to setup an Amazon affiliate link.  People are much more likely to buy a book based on a review from a trusted source.  I always try to buy through a referral link if there is one. Amazon pays about 4% of the price as a referral fee.  You also get credit for anything else they buy while on the site.  I recently had someone buy an iPod nano with their SQL Server book making me an extra $5.60 richer!  Estimating how much you can make is difficult though.  How much attention you draw to the links and book reviews can dramatically affect the earnings. Private Ad Sales This is the hardest but potentially most lucrative option.  You sell advertising directly to companies that want to sell things to your readers.  Typically this would be SQL Server tool vendors, hosting companies or anyone else that wants to make money off database administrators.  This is also the most difficult to do.  You’ll need the contacts at the companies and enough page views to make it worth their while.  You’ll also need software to track the page views and clicks, geo-target your ads and smooth out the impressions.  Your earnings are based on whatever you can negotiate with the companies. SQL Server Ad Network For the last couple of years I’ve run any extra ads that I sold on the SQLTeam Weblogs.  You can see an example of that on Mladen’s blog.  The ad in the upper right corner is one that I’m running for him.  (Note: Many of the ads I’m running are geo-targeted to only appear in English speaking countries.  You may see a different set of ads outside the US, Canada and the UK.  You can also see he has a couple of Google ads on his blog.)  When I run ads on his blog I split the advertising revenue with him.  They make a little and I make a little. I recently started to expand this and sell advertising specifically to run on SQL Server-related blogs.  I’m also starting to run ads on non-SQLTeam blogs.  The only way I can sell more advertising is to have more blogs to run it on.  And that’s where you come in. I’ve created a SQL Server advertising network.  I handle all the ad sales and provide the technology to serve the ads.  I handle collections and payments back to you.  You get paid at the end of each month regardless of when (or if) the advertiser actually pays.  All you need to do is add a small piece of JavaScript to your site to display the ads. If you’re writing about SQL Server and interested in earning a little money for your site I’d like to talk to you.  You can use the Contact Us page on SQLTeam.com to reach me.  Running advertising on your blog isn’t for everyone.  If you’re concerned about what advertisers might think about certain posts then you might not be a good fit.  For the most part this isn’t an issue.  You’ll also need to have a PayPal account to receive payments.  You probably won’t get rich doing this.  But you can earn extra cash on the side for doing what you would do anyway.  I do know that people have earned enough to buy themselves a nice laptop doing this. My initial target is blogs with more than 10,000 page views per month.  I expect to pay two to three times what Google pays.  If you have less than 10,000 page views per month but are still interested I’d still like to hear from you.  I may not be able to sign up smaller blogs right away but we’ll get the process started.  If you’re unsure about your traffic Google Analytics is a free tool that provides great reporting on traffic, popular posts and how people find your blog.  If you have any questions or are just curious drop me a line and I’ll try to answer your questions.

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  • PASS Summit book launch and meet the authors - Professional SQL Server 2012 Internals & Troubleshooting

    - by Christian
    I’m very pleased to announce that we’ll be officially launching our new book, Professional SQL Server 2012 Internals and Troubleshooting at the PASS Summit in Seattle tomorrow. In partnership with our great friends at SQL Sentry we’ll have most of the authors at the SQL Sentry exhibitors stand from 12:30 on Thursday 8th November for a book signing event which will give you a rare opportunity to meet with the authors and contributors, many of which have flown in from around the world. SQL Sentry also have lots and lots of copies to give away for free so be sure to drop by their stand and ask about it! If you really can’t wait or run the risk of not getting a copy then the PASS bookstore has a few copies for sale but don’t expect them to be there for long! You can also order it from your favourite online retailer: amazon.com: http://amzn.to/U9IlPV barnesandnoble.com: http://bitly.com/Ux1gog amazon.co.uk: http://bitly.com/WBJ18l I’ll be writing a follow-up post very soon explaining why I think you should buy this book so look out for it!   Christian Bolton - MCA, MCM, MVP Technical Director http://coeo.com - SQL Server Consulting & Managed Services

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  • DIY Arcade Build Packed into an IKEA Console Table

    - by Jason Fitzpatrick
    If you checked out the Raspberry Pi-powered arcade table we shared earlier this week but want an all-in-one solution that doesn’t require as much configuration, this table uses a pre-programmed board that comes loaded with arcade classics. Courtesy of tinker Casper36, we’re treated to a compact build hidden inside an IKEA console table. One of the most polished aspects of this build is how well hidden the flush-mounted screen is under the dark glass tabletop–when the screen it just looks like the table has a patterned glass insert. Hit up the link below for the full photo build-log. IKEA Console Arcade Build [via Make] 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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