SQL Server Query: Fast with Literal but Slow with Variable

Question

I have a view that returns 2 ints from a table using a CTE. If I query the view like this it runs in less than a second

SELECT * FROM view1 WHERE ID = 1
         


        

Answer 1

Came across this same issue myself and it turned out to be a missing index involving a (left) join on the result of a subquery.

select *
from foo A
left outer join (
  select x, count(*)
  from bar
  group by x
) B on A.x = B.x

Added an index named bar_x for bar.x