Re: [SQL] Query tuning

2008-05-16 Thread Simon Riggs 

On Fri, 2008-05-16 at 09:21 -0600, Scott Marlowe wrote:
 On Thu, May 15, 2008 at 12:00 AM,  [EMAIL PROTECTED] wrote:
  Hi,
 
  select count(distinct(j.JOBID)) as jobCount
  from  JOB_TYPE_FIRST a, JOB_TYPE_SECOND b, JOB_ALLOCATION_WORKLIST j
  where (( a.JOBID = j.JOBID)
  and (a.BOOK_ID = :bookId))
  or ((b.JOBID = j.JOBID)
  and (b.BOOK_ID = :bookId));
 
 Have you tried joining a with j and b with j separately, and then
 doing a union on those two sets?

That seems the only way to get a sane answer to this query, which is
otherwise an unconstrained join on both sides of the OR. Great example
of a query which runs slow because the question is phrased incorrectly.
Count(distinct) is pretty much the only function that will give the same
answer as a correctly phrased query.

-- 
 Simon Riggs   www.2ndQuadrant.com
 PostgreSQL Training, Services and Support


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[SQL] Query tuning

2008-05-15 Thread kapil.munish 
Hi,





I have a query which is run across 3 tables JOB_TYPE_FIRST,
JOB_TYPE_SECOND and JOB_ALLOCATION_WORKLIST.



The column JOBID is referenced in JOB_ALLOCATION_WORKLIST table and
primary key in both JOB_TYPE_FIRST, JOB_TYPE_SECOND tables.



There is one more column BOOK_ID which is supplied as the binding
parameter to the query. The query looks like:



select count(distinct(j.JOBID)) as jobCount

from  JOB_TYPE_FIRST a, JOB_TYPE_SECOND b, JOB_ALLOCATION_WORKLIST j

where (( a.JOBID = j.JOBID)

and (a.BOOK_ID = :bookId))

or ((b.JOBID = j.JOBID)

and (b.BOOK_ID = :bookId));



As the records in the database are too large it is having huge cost and
stalling the server and takes lot of time.



Can anyone suggest a better way to fetch the results for the query or
tune it? Any help would be highly appreciated.





Thanks  Regards,

Kapil


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