Sql parameter value that may or may not be null

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SQL-Server-2008

I am using MS Sql Server 2008. My query has the code

SQL

WHERE RepCode = @RepCode

When @RepCode is set to a non-null value, the query behaves as I would expect. When I set the parameter to DBNull.Value, the query returns nothing, even though there is data that should be returned. If I rewrite it

SQL

WHERE RepCode IS @RepCode

then the query works correctly for a null value but not for a non-null value.

I assume that there is some way to write a parameterized query where the parameter may or may not be null that will always return the correct value. How would I do this?

Posted 7-Sep-11 10:11am

Gregory Gadow

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Solution 2

It doesn't help you specifically, but MySQL has the <=> operator, called the "Null-safe equal-to" operator, or the "spaceship" operator.

I don't think T-SQL has this :(

Posted 7-Sep-11 10:37am

Yvan Rodrigues

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Wendelius · Accepted Answer · 2011-09-07T10:21:00

You have pretty much discovered the reason for the problem. NULL is never equal to anything, not even to another NULL.

One workaround for this is that you eliminate NULL's from the comparison by replacing it with another value. Perhaps the easiest way is to use COALESCE[^]. Using that, your example would be something like:

SQL

WHERE COALESCE(RepCode, -1) = COALESCE(@RepCode, -1)

So the idea is that you replace the NULL with some other value.

Important: Just make sure that the value does not exist in the data since that would bring false results.