Question

I have a stored procedure on SQL Server 2005. It is pulling from a Table function, and has two joins. When the query is run using a load test it kills the CPU 100% across all 16 cores! I have determined that removing one of the joins makes the query run fine, but both taxes the CPU.

 Select 
  SKey
 From 
  dbo.tfnGetLatest(@ID) a 
  left join [STAGING].dbo.RefSrvc b on 
   a.LID = b.ESIID
  left join [STAGING].dbo.RefSrvc c on 
   a.EID = c.ESIID 

Any help is appreciated, note the join is happening on the same table in a different database on the same server.

Answer 1

This may shed some light on the problem. Can you separate the first join out into a CTE?

Something like this:

with FirstJoin(SKey,EID) as (
   select a.Skey,a.EID from 
       dbo.tfnGetLatest(@ID) a 
       left join [STAGING].dbo.RefSrvc b on a.LID = b.ESIID
)

select Skey from FirstJoin fj
left join [STAGING].dbo.RefSrvc c on fj.EID = c.ESIID

Also, since both of your joins are left joins how do they narrow the result set? Isn’t that query equivalent to select sKey from dbo.tfnGetLatest(@ID)?