Question

I have a SQL query which is written in string and then executed using command Exec(string) like the following :

Declare @TestId bigint = null
Declare @Query nvarchar(max)
set @Query = 'SELECT * from Registrations where RegistrationId = 15 AND (' + CAST(@TestId AS NVARCHAR) + ' IS NULL OR TestId = ' + CAST(@TestId AS NVARCHAR) + ') '
EXEC(@Query)

The problem now that the IS NULL is not parsed correctly inside the string but when i remove the IS NULL from the string it works correctly and when the @TestId takes a value other than null it works correctly where the problem now is in the casting of the IS NULL inside the @Query string.

Note : @TestId is a procedure parameter

I need to know how to make the SQL feel with the IS NULL and parse it correctly

Thanks in advance

Answer 1

If you really do need to use dynamic sql for this, use sp_executesql like this:

Declare @TestId bigint = null
Declare @Query nvarchar(max)
set @Query = 'SELECT * from Registrations where RegistrationId = 15 AND (@TestId IS NULL OR TestId = @TestId)'

EXECUTE sp_executesql @Query, N'@TestId BIG INT', @TestId