Question

I am trying to optimize the speed of a query which uses a redundant query block. I am trying to do a row-wise join in sql server 2008 using the query below.

Select * from 
(<complex subquery>) cq
join table1 t1 on (cq.id=t1.id)
union
Select * from  
<complex subquery> cq
join table2 t2 on (cq.id=t2.id)

The <complex subquery> is exactly the same on both the union sub query pieces except we need to join it with multiple different tables to obtain the same columnar data.

Is there any way i can either rewrite the query to make it faster without using a temporary table to cache results?

Answer 1

Why not use a temporary table and see if that improves the execution stats?

In some circumstances the Query Optimizer will automatically add a spool to the plan that caches sub queries this is basically just a temporary table though.

Have you checked your current plan to be sure that the query is actually being evaluated more than once?