I have a query on a large table that looks like this:
declare @myIdParam int = 1 select * from myTable where (@myIdParam is null or myTable.Id = @myIdParam)
There are several similar conditionals like this in the where clause, and there are also a lot of joins, but this is a summary.
Effectively, if @myIdParam is null, we do not want to restrict the results using this parameter.
I am not a DB pro, but from my tests it seems like this NULL check is done for every record and not optimized out in any way.
If I remove the null check and assume the parameter is not null, the query returns instantly. Otherwise, it takes up to ten seconds.
Is there a way to optimize this so the check is done only once at runtime?