Hvordan genbruger man en underforespørgsel i sql?

Brug et fælles tabeludtryk (CTE), hvis du bruger SQL Server 2005+:

with cte as (
      select columns
      from result_set
      where condition_common
    )
select columns
from cte  as subset1
      join
      cte as subset2 
         on subset1.somekey = subset2.somekey
where otherconditions