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Editorial Team
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Asked: 2026-05-27T13:01:16+00:00

I remember reading a while back that randomly SQL Server can slow down and

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I remember reading a while back that randomly SQL Server can slow down and / or take a stupidly long time to execute a stored procedure when it is written like:

CREATE PROCEDURE spMyExampleProc
(
   @myParameterINT
)
AS
BEGIN

   SELECT something FROM myTable WHERE myColumn = @myParameter

END

The way to fix this error is to do this:

CREATE PROCEDURE spMyExampleProc
(
   @myParameterINT
)
AS
BEGIN
   DECLARE @newParameter INT
   SET @newParameter = @myParameter

   SELECT something FROM myTable WHERE myColumn = @newParameter 
END

Now my question is firstly is it bad practice to follow the second example for all my stored procedures? This seems like a bug that could be easily prevented with little work, but would there be any drawbacks to doing this and if so why?

When I read about this the problem was that the same proc would take varying times to execute depending on the value in the parameter, if anyone can tell me what this problem is called / why it occurs I would be really grateful, I cant seem to find the link to the post anywhere and it seems like a problem that could occur for our company.

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1 Answer

  1. Editorial Team

    You could always use the this masking pattern but it isn’t always needed. For example, a simple select by unique key, with no child tables or other filters should behave as expected every time.

    Since SQL Server 2008, you can also use the OPTIMISE FOR UNKNOWN (SO). Also see Alternative to using local variables in a where clause and Experience with when to use OPTIMIZE FOR UNKNOWN

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