Thanks Sergey ;)

>Hi Eric
>
>Sorry, I misread your original post. Try

>DECLARE @IdList varchar(8000)
>SELECT @IdList = ISNULL(@IdList + ', ', '') + StudentId
>	FROM survey
>	WHERE StudentId IN ( SELECT StudentId FROM survey
>		WHERE interest IN (3,45)
>		GROUP BY StudentId
>		HAVING COUNT(*) = 2 )
>GROUP BY StudentId
>SELECT @IdList

As you can see, ther are two "variables" in this query: the list of interests '(3,45)' and number of valuses in the list - '2'.
>
>