-- set @my_var = @my_val IF ALL values in a specified col(s) of @table1
-- also exist in a specified col(s) of @table2
-- OTHERWISE, set @my_var = 0
SET @my_var = CASE
WHEN NOT EXISTS (
SELECT my_col FROM @table1
EXCEPT                
SELECT my_col FROM @table2
THEN @my_val
ELSE 0
END