TSQL Variable With List of Values for IN Clause

Question

I want to use a clause along the lines of \"CASE WHEN ... THEN 1 ELSE 0 END\" in a select statement. The tricky part is that I need it to work with \"value IN @List\".

Answer 1

You can use a variable in an IN clause, but not in the way you're trying to do. For instance, you could do this:

declare @i int
declare @j int

select @i = 10, @j = 20

select * from YourTable where SomeColumn IN (@i, @j)

The key is that the variables cannot represent more than one value.

To answer your question, use the inline select. As long as you don't reference an outer value in the query (which could change the results on a per-row basis), the engine will not repeatedly select the same data from the table.