Multiple Active Result Sets (MARS) was added specifically for this type of operation so that you don&#39;t have to have two connections open at the same time to be able to read from a SqlDataReader AND execute additional batches. 

MARS is compatible with SQL Server 2005 and above. To quote from MSDN docs:

&gt; Before the introduction of Multiple
&gt; Active Result Sets (MARS), developers
&gt; had to use either multiple connections
&gt; or server-side cursors to solve
&gt; certain scenarios.

For more info see:

&gt;[MSDN Library - MARS Overview][1]

Worked example reading and updating data:

&gt;[MSDN Library - Manipulating Data (MARS)][2] scroll down to &#39;Reading and Updating Data with MARS&#39;




  [1]: http://msdn.microsoft.com/en-gb/library/cfa084cz.aspx
  [2]: http://msdn.microsoft.com/en-gb/library/yf1a7f4f.aspx

This is as far as I know the reason MARS was added, so yeah I think you should use it. 

Best way to test this is to fire SQLServer Profiler, and see what really happens on the server side. 

My guess is that it will not be better since you are using ExecuteNonQuery(). So, in fact, you don&#39;t work with multiple results. 

I&#39;d like a daemonizer that can turn an arbitrary, generic script or command into a &lt;a href=&quot;http://en.wikipedia.org/wiki/Daemon_(computer_software)&quot;&gt;daemon&lt;/a&gt;.

There are two common cases I&#39;d like to deal with:

 1. I have a script that should run forever.  If it ever dies (or on reboot), restart it.  Don&#39;t let there ever be two copies running at once (detect if a copy is already running and don&#39;t launch it in that case).

 2. I have a simple script or command line command that I&#39;d like to keep executing repeatedly forever (with a short pause between runs).  Again, don&#39;t allow two copies of the script to ever be running at once.

Of course it&#39;s trivial to write a &quot;while(true)&quot; loop around the script in case 2 and then apply a solution for case 1, but a more general solution will just solve case 2 directly since that applies to the script in case 1 as well (you may just want a shorter or no pause if the script is not intended to ever die (of course if the script really *does* never die then the pause doesn&#39;t actually matter)).

Note that the solution should not involve, say, adding file-locking code or PID recording to the existing scripts.

More specifically, I&#39;d like a program &quot;daemonize&quot; that I can run like

    % daemonize myscript arg1 arg2

or, for example, 

    % daemonize &#39;echo `date` &gt;&gt; /tmp/times.txt&#39;

which would keep a growing list of dates appended to times.txt. (Note that if the argument(s) to daemonize is a script that runs forever as in case 1 above, then daemonize will still do the right thing, restarting it when necessary.)  I could then put a command like above in my .login and/or cron it hourly or minutely (depending on how worried I was about it dying unexpectedly).

NB: The daemonize script will need to remember the command string it is daemonizing so that if the same command string is daemonized again it does not launch a second copy.

Also, the solution should ideally work on both OS X and linux but solutions for one or the other are welcome.

EDIT: It&#39;s fine if you have to invoke it with `sudo daemonize myscript myargs`.

(If I&#39;m thinking of this all wrong or there are quick-and-dirty partial solutions, I&#39;d love to hear that too.)

&lt;hr&gt;

PS: In case it&#39;s useful, [here&#39;s](https://stackoverflow.com/questions/473620/how-do-you-create-a-daemon-in-python) a similar question specific to python.



And [this](https://stackoverflow.com/questions/38596/whats-the-best-way-to-keep-a-php-script-running-as-a-daemon/39609#39609) answer to a similar question has what appears to be a useful idiom for a quick-and-dirty demonizing of an arbitrary script:



How do I daemonize an arbitrary script in unix?

I&#39;m trying to do conditional formatting so that the cell color will change if the value is different from the value in the cell left of it (each column is a month, in each row are the expenses on certain object. I want to monitor easily changes in prices over months.)

I can do it per cell and format-drag it, but I would like a general formula to apply to the whole worksheet.

Thanks!

Excel formula to reference &#39;CELL TO THE LEFT&#39;

I have some C# in which I create a reader on a connection (`ExecuteReader`), then for every row in that reader, perform another command (with `ExecuteNonQuery`).  In this case is it better that I use `MultipleActiveResultSets=True` on my connection or use multiple connections?

MultipleActiveResultSets=True or multiple connections?

<p>I have some C# in which I create a reader on a connection (<code>ExecuteReader</code>), then for every row in that reader, perform another command (with <code>ExecuteNonQuery</code>).  In this case is it better that I use <code>MultipleActiveResultSets=True</code> on my connection or use multiple connections?</p>


I&#39;m an entry level programmer so please be descriptive in your responses.

I am trying to use a Java API given as a .jar file in my C# .net application.  I don&#39;t know much Java, but this .jar file says &quot;no main-class manifest attribute&quot; when I try to run it so this means its a library?  This Java API also comes with a .java file which shows how to use the library but I cannot see the code inside the .jar.

I found &lt;a href=&quot;https://stackoverflow.com/questions/171717/using-java-classes-with-c&quot;&gt;this question&lt;/a&gt; on this site, and one of the answers reads, &quot;In simple way you can pack your java classes to jar file then In C# use Process class for execute and map IO stream.&quot;  I am semi-familiar with the Process class in C# but I don&#39;t understand how I could use it to use a Java library in my C# .net project.

Is this possible? or was that answer incorrect?

If so, could you explain how I can use the .jar library in my C# app.

Use a .jar java library API in C#?

In the two following snippets, is the first one safe or must you do the second one?

By safe I mean is each thread guaranteed to call the method on the Foo from the same loop iteration in which the thread was created?

Or must you copy the reference to a new variable &quot;local&quot; to each iteration of the loop?

    var threads = new List&lt;Thread&gt;();
    foreach (Foo f in ListOfFoo)
    {      
        Thread thread = new Thread(() =&gt; f.DoSomething());
        threads.Add(thread);
        thread.Start();
    }

-

    var threads = new List&lt;Thread&gt;();
    foreach (Foo f in ListOfFoo)
    {      
        Foo f2 = f;
        Thread thread = new Thread(() =&gt; f2.DoSomething());
        threads.Add(thread);
        thread.Start();
    }

**Update:** As pointed out in Jon Skeet&#39;s answer, this doesn&#39;t have anything specifically to do with threading.

The foreach identifier and closures

My program need to parse css files into an in-memory object format. Any advice on how this should be done ?


Is there a CSS parser for C#?

In terms of PC development (excluding Xbox and Zune),

What is the difference between XNA and C# DirectX? Does C# DirectX have a significant advantage over XNA (in terms of speed, royalties, etc)?

How are the two compared to the speed unmanaged C++ DirectX?

Where is the industry moving in terms of game programming?

Comparison between XNA and DirectX (C#)

Is it possible to pass parameters with an `HTTP` get request? If so, how should I then do it? I have found an `HTTP` post requst ([link][1]). In that example the string `postData` is sent to a webserver. I would like to do the same using *get* instead. Google found this example on `HTTP` get [here][2]. However no parameters are sent to the web server.


  [1]: http://msdn.microsoft.com/en-us/library/debx8sh9.aspx
  [2]: http://support.microsoft.com/kb/307023

How to make an HTTP get request with parameters

What is going on behind the scenes when you mark a regular expression as one to be compiled? How does this compare/is different from a cached regular expression?

Using this information, how do you determine when the cost of computation is negligible compared to the performance increase?

How does RegexOptions.Compiled work?

I&#39;m using log4net to log write log message to a rolling log file. 

Now I would also redirect all trace messages from &lt;code&gt;System.Diagnostics.Trace&lt;/code&gt; to that log file. How can I configure that? I tried to find anything about that in the log4net documentation, but without success. Is it possible at all?

The reason I want to do that is because I am interested in the Trace messages of a 3rd party library.

&lt;!-- language: xml --&gt;

    &lt;log4net&gt;
        &lt;appender name=&quot;R1&quot; type=&quot;log4net.Appender.RollingFileAppender&quot;&gt;
          &lt;file value=&quot;C:\Logs\MyService.log&quot; /&gt;
          &lt;appendToFile value=&quot;true&quot; /&gt;
          &lt;rollingStyle value=&quot;Date&quot; /&gt;
          &lt;maxSizeRollBackups value=&quot;10&quot; /&gt;
          &lt;datePattern value=&quot;yyyyMMdd&quot; /&gt;
          &lt;layout type=&quot;log4net.Layout.PatternLayout&quot;&gt;
            &lt;conversionPattern value=&quot;%date [%thread] %-5level %logger [%property{NDC}] - %message%newline&quot; /&gt;
          &lt;/layout&gt;
        &lt;/appender&gt;
    &lt;/log4net&gt;

How to log Trace messages with log4net?

I am starting out with unit testing, I have a method that uses the web.config for a connection string.

I was hoping to be able to use

    [DeploymentItem(&quot;web.config&quot;)]

to get the web config file, this still leaves me with null reference exceptions (that&#39;d be what I write my next test for).

How do I use the config file included with the project I am trying to test?

I am using the testing framework included in VS 2008, if that makes any difference.

Thanks




How to use web.config when unit testing an asp .net application

I have some confusion related to the .NET platform build options in Visual Studio 2008.

What is the &quot;Any CPU&quot; compilation target, and what sort of files does it generate? I examined the output executable of this &quot;Any CPU&quot; build and found that they are the x86 executables (who would not see that coming!). So, is there any difference between targeting executable to x86 vs. &quot;Any CPU&quot;?

Another thing that I noticed, is that managed C++ projects do not have this platform as an option. Why is that? Does that mean that my suspicion about &quot;Any CPU&quot; executables being plain 32-bit ones is right?



What does the Visual Studio &quot;Any CPU&quot; target mean?

In my last job, we worked on a very database-heavy application, and I developed some formatting standards so that we would all write SQL with a common layout. We also developed coding standards, but these are more platform-specific so I&#39;ll not go into them here.

I&#39;m interested to know what other people use for SQL formatting standards. Unlike most other coding environments, I haven&#39;t found much of a consensus online for them.

To cover the main query types:
    
    select
    	ST.ColumnName1,
    	JT.ColumnName2,
    	SJT.ColumnName3
    from 
        SourceTable ST
    inner join JoinTable JT
    	on JT.SourceTableID = ST.SourceTableID
    inner join SecondJoinTable SJT
    	on ST.SourceTableID = SJT.SourceTableID
    	and JT.Column3 = SJT.Column4
    where
    	ST.SourceTableID = X
    	and JT.ColumnName3 = Y

There was some disagreement about line feeds after `select`, `from` and `where`. The intention on the select line is to allow other operators such as &quot;top X&quot; without altering the layout. Following on from that, simply keeping a consistent line feed after the key query elements seemed to result in a good level of readability. 

Dropping the linefeed after the `from` and `where` would be an understandable revision. However, in queries such as the `update` below, we see that the line feed after the `where` gives us good column alignment. Similarly, a linefeed after `group by` or `order by` keeps our column layouts clear and easy to read.

    update
    	TargetTable
    set
    	ColumnName1 = @value,
    	ColumnName2 = @value2
    where
    	Condition1 = @test

Finally, an `insert`:

    insert into TargetTable (
    	ColumnName1,
    	ColumnName2,
    	ColumnName3
    ) values (
    	@value1,
    	@value2,
    	@value3
    )

For the most part, these don&#39;t deviate that far from the way MS [SQL Server Managements Studio][1] / query analyser write out SQL, however they *do* differ.

I look forward to seeing whether there is any consensus in the Stack Overflow community on this topic. I&#39;m constantly amazed how many developers can follow standard formatting for other languages and suddenly go so random when hitting SQL.

  [1]: http://en.wikipedia.org/wiki/SQL_Server_Management_Studio


SQL formatting standards

I backed up a database:

    BACKUP DATABASE MyDatabase
    TO DISK = &#39;MyDatabase.bak&#39;
    WITH INIT --overwrite existing

And then tried to restore it:

    RESTORE DATABASE MyDatabase
       FROM DISK = &#39;MyDatabase.bak&#39;
       WITH REPLACE --force restore over specified database

And now the database is stuck in the restoring state.

Some people have theorized that it&#39;s because there was no log file in the backup, and it needed to be rolled forward using:

    RESTORE DATABASE MyDatabase
    WITH RECOVERY 

Except that, of course, fails:

    Msg 4333, Level 16, State 1, Line 1
    The database cannot be recovered because the log was not restored.
    Msg 3013, Level 16, State 1, Line 1
    RESTORE DATABASE is terminating abnormally.


And exactly what you want in a catastrophic situation is a restore that won&#39;t work.


----------

The backup contains both a data and log file:

    RESTORE FILELISTONLY 
    FROM DISK = &#39;MyDatabase.bak&#39;

    Logical Name    PhysicalName
    =============   ===============
    MyDatabase	  C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\DATA\MyDatabase.mdf
    MyDatabase_log  C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\DATA\MyDatabase_log.LDF

SQL Server: Database stuck in &quot;Restoring&quot; state

I&#39;m looking at the AdventureWorks sample database for SQL Server 2008, and I see in their creation scripts that they tend to use the following:

    ALTER TABLE [Production].[ProductCostHistory] WITH CHECK ADD 
    CONSTRAINT [FK_ProductCostHistory_Product_ProductID] FOREIGN KEY([ProductID])
      REFERENCES [Production].[Product] ([ProductID])
    GO

followed immediately by :

    ALTER TABLE [Production].[ProductCostHistory] CHECK CONSTRAINT     
    [FK_ProductCostHistory_Product_ProductID]
    GO

I see this for foreign keys (as here), unique constraints and regular `CHECK` constraints; `DEFAULT` constraints use the regular format I am more familiar with such as:

    ALTER TABLE [Production].[ProductCostHistory] ADD  CONSTRAINT  
    [DF_ProductCostHistory_ModifiedDate]  DEFAULT (getdate()) FOR [ModifiedDate]
    GO

What is the difference, if any, between doing it the first way versus the second?

WITH CHECK ADD CONSTRAINT followed by CHECK CONSTRAINT vs. ADD CONSTRAINT

Is there any way in which I can clean a database in SQl Server 2005 by dropping all the tables and deleting stored procedures, triggers, constraints and all the dependencies in one SQL statement?


**REASON FOR REQUEST:**

I want to have a DB script for cleaning up an existing DB which is not in use rather than creating new ones, especially when you have to put in a request to your DB admin and wait for a while to get it done!

Drop all the tables, stored procedures, triggers, constraints and all the dependencies in one sql statement

I want to store times in a database table but only need to store the hours and minutes.
I know I could just use DATETIME and ignore the other components of the date, but what&#39;s the best way to do this without storing more info than I actually need?

Best way to store time (hh:mm) in a database

I&#39;m no beginner to using SQL databases, and in particular SQL Server.  However, I&#39;ve been primarily a SQL 2000 guy and I&#39;ve always been confused by schemas in 2005+.  Yes, I know the basic definition of a schema, but what are they really used for in a typical SQL Server deployment?

I&#39;ve always just used the default schema.  Why would I want to create specialized schemas?  Why would I assign any of the built-in schemas?

EDIT: To clarify, I guess I&#39;m looking for the benefits of schemas.  If you&#39;re only going to use it as a security scheme, it seems like database roles already filled that.. er.. um.. role.  And using it a as a namespace specifier seems to have been something you could have done with ownership (dbo versus user, etc..).

I guess what I&#39;m getting at is, what do Schemas do that you couldn&#39;t do with owners and roles?  What are their specifc benefits?

What good are SQL Server schemas?

I&#39;m trying to determine the relative performance of two different queries and have two ways of measuring this available to me:  
1. Run both and time each query  
2. Run both and get &quot;Query Cost&quot; from the actual execution plan

Here is the code I run to time the queries...

    DBCC FREEPROCCACHE
    GO
    DBCC DROPCLEANBUFFERS
    GO
    DECLARE @start DATETIME SET @start = getDate()
    EXEC test_1a
    SELECT getDate() - @start AS Execution_Time
    GO
    
    DBCC FREEPROCCACHE
    GO
    DBCC DROPCLEANBUFFERS
    GO
    DECLARE @start DATETIME SET @start = getDate()
    EXEC test_1b
    SELECT getDate() - @start AS Execution_Time
    GO

What I get is the following:

    Stored_Proc     Execution_Time     Query Cost (Relative To Batch)

    test_1a         1.673 seconds      17%
    test_1b         1.033 seconds      83%


The results of the execution time directly contradict the results of the Query Cost, but I&#39;m having difficulty determining what &quot;Query Cost&quot; actually means.  My best guess is that it is an aggregate of Reads/Writes/CPU_Time/etc, so I guess I have a couple of questions:  
  
1. Is there a definative source to explain what this measure means?  
  
2. What other &quot;Query Performance&quot; metrics do people use, and what are their relative merits?

&lt;br&gt;
It may be important to note that this is a medium sized SQL Server, running MS SQL Server 2005 on MS Server 2003 Enterprise Edition with multiple processors and 100+ concurrent users.



EDIT:

After some bother I managed to get Profiler access on that SQL Server, and can give extra info (Which supports Query Cost being related to system resources, not Execution Time itself...)

    Stored_Proc    CPU      Reads    Writes   Duration   

    test_1a        1313     3975     93       1386
    test_1b        2297     49839    93       1207

Impressive that taking more CPU with MANY more Reads takes less time :)

Measuring Query Performance : &quot;Execution Plan Query Cost&quot; vs &quot;Time Taken&quot;

I am trying to insert all values of one table into another. But the insert statement accepts values, but i would like it to accept a select * from the initial_Table. Is this possible?

Insert all values of a table into another table in SQL

I have a project in SSIS and I&#39;ve added an Execute SQL Task which sends its result out to a variable. I wanted to confirm the value because I was worried that it would try to write it out as a resultset object rather than an actual integer (in this case I&#39;m returning a COUNT).

My first thought was just to run it in debug mode and add the global variable to my Watch window. Unfortunately, when I right-click on the Watch window, the option to &quot;Add Variable&quot; is greyed out. What am I missing here?

I&#39;ve gotten around confirming that my variable is set correctly, so I&#39;m not interested in methods like putting a script in to do a MsgBox with the value or anything like that. For future reference I&#39;d like to be able to watch variables in debug mode. If there are some kind of constraints on that then I&#39;d like to know the what and why of it all if anyone knows.

The help is woefully inadequate on this one and every &quot;tutorial&quot; that I can find just says, &quot;Add the variable to the Watch window and debug&quot; as though there should never be a problem doing that.

Thanks for any insight!

Watching variables in SSIS during debug

I [added a new ADO.Net Entity Data Model][1] into my project and used the [Update Wizard][2] to add tables into the model.  Five of the selected tables were added to the design surface.  Two other tables will not add.  I select them in the wizard and click Finish, yet they never show up on the design surface.

Is this a bug, or are there some situations where a table cannot be added to the model (by design)?

&lt;hr /&gt;

UPDATE: The XML (*.edmx) reveals the problem.  

    &lt;!--Errors Found During Generation:
    warning 6013: The table/view &#39;FooBar.dbo.Roles&#39; does not 
    have a primary key defined and no valid primary key could be inferred. 
    This table/view has been excluded. To use the entity you will need to 
    review your schema, add the correct keys and uncomment it.--&gt;
    &lt;!--&lt;EntityType Name=&quot;Roles&quot;&gt;
        &lt;Property Name=&quot;role_id&quot; Type=&quot;decimal&quot; /&gt;
        &lt;Property Name=&quot;role_desc&quot; Type=&quot;nvarchar&quot; MaxLength=&quot;30&quot; /&gt;
    &lt;/EntityType&gt;--&gt;

  [1]: https://i.stack.imgur.com/5CduL.png
  [2]: https://i.stack.imgur.com/c4Pju.png

ADO.NET Entity Framework: Update Wizard will not add tables

I have the following code:
            
    const string Sql = 
        @&quot;select distinct [name] 
          from tblCustomers 
          left outer join tblCustomerInfo on tblCustomers.Id = tblCustomerInfo.CustomerId  
          where (tblCustomer.Name LIKE &#39;%@SEARCH%&#39; OR tblCustomerInfo.Info LIKE &#39;%@SEARCH%&#39;);&quot;;
                        
    using (var command = new SqlCommand(Sql, Connection))
    {       
        command.Parameters.AddWithValue(&quot;@SEARCH&quot;, searchString);
        ...
    }

This does not work, I tried this as well:

    const string Sql = 
        @&quot;select distinct [name] 
         from tblCustomers 
         left outer join tblCustomerInfo on tblCustomers.Id = tblCustomerInfo.CustomerId  
         where (tblCustomer.Name LIKE @SEARCH OR tblCustomerInfo.Info LIKE @SEARCH );&quot;;
                              
    using (var command = new SqlCommand(Sql, Connection))
    {       
        command.Parameters.AddWithValue(&quot;@SEARCH&quot;, &quot;&#39;%&quot; + searchString + &quot;%&#39;&quot;);
        ...
    }

but this does not work as well. What is going wrong? Any suggestions?


Use of SqlParameter in SQL LIKE clause not working

After connecting to the database, can I get the name of all the columns that were returned in my `SqlDataReader`?


Can you get the column names from a SqlDataReader?

I want to execute a query like this

 

       var result = from entry in table
                         where entry.something == null
                         select entry;

and get an `IS NULL` generated. 

Edited:
After the first two answers i feel the need to clarify that I&#39;m using Entity Framework
and not Linq to SQL. The object.Equals() method does not seem to work in EF.

Edit no.2:
The above query works as intended. It correctly generates `IS NULL`. My production code however was
 

    value = null;
    var result = from entry in table
                             where entry.something == value
                             select entry;
and the generated SQL was `something = @p; @p = NULL`. It seems that EF correctly translates the constant expression but if a variable is involved it treats it just like a normal comparison. Makes sense actually. I will close this question.

How can I query for null values in entity framework?

All of a sudden I keep getting a `MetadataException` on instantiating my generated `ObjectContext` class. The connection string in App.Config looks correct - hasn&#39;t changed since last it worked - and I&#39;ve tried regenerating a new model (edmx-file) from the underlying database with no change.

Anyone have any ideas?

Further details: I haven&#39;t changed any properties, I haven&#39;t changed the name of any output assemblies, I haven&#39;t tried to embed the EDMX in the assembly. I&#39;ve merely waited 10 hours from leaving work until I got back. And then it wasn&#39;t working anymore.

I&#39;ve tried recreating the EDMX. I&#39;ve tried recreating the project. I&#39;ve even tried recreating the database, from scratch. No luck, whatsoever.

Content Type	Original Author	Original Content on Stackoverflow
Question	Sprintstar	View Question on Stackoverflow
Solution 1 - C#	Kev	View Answer on Stackoverflow
Solution 2 - C#	Rune Grimstad	View Answer on Stackoverflow
Solution 3 - C#	dmajkic	View Answer on Stackoverflow

MultipleActiveResultSets=True or multiple connections?

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

Excel formula to reference 'CELL TO THE LEFT'

How do I daemonize an arbitrary script in unix?

Attributions