Sunday, 6 March 2016

SET NOCOUNT ON Improves SQL Server Stored Procedure Performance

One of the biggest things that DBAs try to do on a daily basis is to ensure that their database systems run as fast as possible. As more and more users access the databases and the databases continue to grow, performance slow downs are almost inevitable. Based on this, DBAs and developers should do everything they possibly can to keep performance related issues in mind early in the database lifecycle. This is not always easy to do, because of the unknowns and the changes that occur over time, but there are some simple things that can be done and we will touch upon one of these in this tip.
Sometimes even the simplest things can make a difference. One of these simple items that should be part of every stored procedure is SET NOCOUNT ON. This one line of code, put at the top of a stored procedure turns off the messages that SQL Server sends back to the client after each T-SQL statement is executed. This is performed for all SELECT, INSERT, UPDATE, and DELETE statements. Having this information is handy when you run a T-SQL statement in a query window, but when stored procedures are run there is no need for this information to be passed back to the client.
By removing this extra overhead from the network it can greatly improve overall performance for your database and application.
If you still need to get the number of rows affected by the T-SQL statement that is executing you can still use the @@ROWCOUNToption. By issuing a SET NOCOUNT ON this function (@@ROWCOUNT) still works and can still be used in your stored procedures to identify how many rows were affected by the statement.
Microsoft even realized the issue that this creates and has changed the stored procedure templates from SQL Server 2000 to SQL Server 2005.
Here is the old template style available in SQL Server 2000 without the SET NOCOUNT ON.
-- =============================================
-- Create procedure basic template
-- =============================================
-- creating the store procedure
FROM sysobjects
WHERE name = N'<procedure_name, sysname, proc_test>' 
AND type = 'P')
DROP PROCEDURE <procedure_name, sysname, proc_test>

CREATE PROCEDURE <procedure_name, sysname, proc_test> 
<@param1, sysname, @p1> <datatype_for_param1, , int> = <default_value_for_param1, , 0>, 
<@param2, sysname, @p2> <datatype_for_param2, , int> = <default_value_for_param2, , 0>
SELECT @p1, @p2

-- =============================================
-- example to execute the store procedure
-- =============================================
EXECUTE <procedure_name, sysname, proc_test> <value_for_param1, , 1>, <value_for_param2, , 2>
Here is the new template style available in SQL Server 2005 with the SET NOCOUNT ON.
-- ================================================
-- Template generated from Template Explorer using:
-- Create Procedure (New Menu).SQL
-- Use the Specify Values for Template Parameters
-- command (Ctrl-Shift-M) to fill in the parameter
-- values below.
-- This block of comments will not be included in
-- the definition of the procedure.
-- ================================================
-- =============================================
-- Author: <Author,,Name>
-- Create date: <Create Date,,>
-- Description: <Description,,>
-- =============================================
CREATE PROCEDURE <Procedure_Name, sysname, ProcedureName>
-- Add the parameters for the stored procedure here
<@Param1, sysname, @p1> <Datatype_For_Param1, , int> = <Default_Value_For_Param1, , 0>,
<@Param2, sysname, @p2> <Datatype_For_Param2, , int> = <Default_Value_For_Param2, , 0>
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.

-- Insert statements for procedure here
SELECT <@Param1, sysname, @p1>, <@Param2, sysname, @p2>
As you can see even simple little things such as this can make an overall improvement for your 
database environment. Stay tuned for other simple tricks and techniques to improve performance.