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                                                                                                                          Nothing shocks me, I am a Software Engineer.

SET NOCOUNT (Transact-SQL)

Posted by Virendra Dugar on January 6, 2009

Whenever we write any procedure and execute it a message appears in message window that shows no of rows affected with the statement written in the procedure and we become very happy to see that our procedure is working. But do you know that this message creates an extra overhead on the network? Yes it does.

By removing this extra overhead from the network, we can actually improve the performance of our database and our application.

How should we do it?
When you create any procedure then first line of your procedure should be

SET NOCOUNT ON;

This one line of code turns off the message that SQL server sends back to front end after every T-SQL statement is executed. This is applied for all SELECT, INSERT, UPDATE and DELETE statements. As when stored procedures are executed there is no need to pass this information back to front end.

When SET NOCOUNT is ON, the count is not returned. When SET NOCOUNT is OFF, the count is returned.If we still need to get the count of no of rows affected, we can still use @@ROWCOUNT option. Because The @@ROWCOUNT function is updated even when SET NOCOUNT is ON.

The setting specified by SET NOCOUNT is in effect at execute or run time and not at parse time.

Microsoft even realized the issue that this creates and has changed the stored procedure templates from SQL Server 2000 to SQL Server 2005.

Template used in SQL SERVER 2005

================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
— =============================================
— Author: 
— Create date: 
— Description: 
— =============================================
CREATE PROCEDURE 
— Add the parameters for the stored procedure here
<@Param1, sysname, @p1> = ,
<@Param2, sysname, @p2> = 
AS
BEGIN
— SET NOCOUNT ON added to prevent extra result sets from
— interfering with SELECT statements.
SET NOCOUNT ON;

— Insert statements for procedure here
SELECT <@Param1, sysname, @p1>, <@Param2, sysname, @p2>
END
GO

================================================

Setting SET NOCOUNT to ON can provide a significant performance boost, because network traffic is greatly reduced.

Enjoy….

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