From: | "tamsin" <tg_mail(at)bryncadfan(dot)co(dot)uk> |
---|---|
To: | <pgsql-general(at)postgresql(dot)org> |
Subject: | RE: |
Date: | 2001-06-29 12:40:04 |
Message-ID: | NEBBKHBOBMJCHDMGKCNJGEFFDAAA.tg_mail@bryncadfan.co.uk |
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Lists: | pgsql-general pgsql-sql |
i think performance is better in postgres if you rewrite this sort of query
as:
select * from purchasemaster where exists (select 1 from itemmaster where
itempriority = 2 and transactionid = purchasemaster.transactionid)
hope this helps,
tamsin
-----Original Message-----
From: pgsql-general-owner(at)postgresql(dot)org
[mailto:pgsql-general-owner(at)postgresql(dot)org]On Behalf Of Kapil Tilwani
Sent: 28 May 2001 12:27
To: pgsql-general(at)postgresql(dot)org; pgsql-sql(at)postgresql(dot)org
Subject: [GENERAL]
Hi,
I have two tables purchasemaster (Master) and ItemMaster (child) linked
through TransactionID
I have a query like
select * from purchasemaster where transactionid in (select transactionid
from itemmaster where itempriority = 2)
****I need this query for MS-Access, MS-SQL and Postgres. Because the
application is supposed to be such that for upto 2-3 users, the application
would be running on MS-Access or MSDE, while for heavier databases i.e.,
greater than 4 , the ideal database would be Postgres
Only the problem is ... (correct me if i am wrong, PLEEEEEEEEEEEASE) that
for each tuple in purchasemaster the sub-query is re-evaluated (True or
False????). What I am looking at is whether it is possible to execute the
query in the sub-query just once, get its value as in "(1,2,5,23,7,90)",
etc. in place of the sub-query and accordingly, execute the main query.
Thank you,
Kapil
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