From: Ken Corey <ken@kencorey.com>
To: Diehl, Jeffrey <jdiehl@sandia.gov>
Cc: pgsql-sql@postgresql.org
Cc: pgsql-general@postgresql.org
Subject: Re: Help with query. (*)
Date: Wed, 17 Jan 2001 19:34:05 +0000
Message-ID: <3A65F3AD.7FDA0A49@kencorey.com> (raw)
References: <B51F0C636E578A4E832D3958690CD73E0130BD9A@es04snlnt>
[NOTE: I'm a pgsql newbie myself. Take this reply with a large-ish
grain of salt!)
Shouldn't it be something straightforward like:
select a.a, a.b, a.c, ...
from a a,
b b
where a.x = b.x,
and a.y = b.y, ... (I'd watch out for too many clauses here...
if you've got a lot of clauses, you're probably not normalized
as much as you should be.)
If you have indexes on the relevant fields, you shouldn't get a table
scan and this should return rather quickly, right?
-Ken
"Diehl, Jeffrey" wrote:
>
> I'm having difficulty writing a query which I really can't live without...
>
> I need to get a list of records from table A for which there are
> corresponding records in table B. I've tried to use the intersect clause,
> but it doesn't seem to work, or it runs far too long. For example:
>
> select * from A
> where 1=1
> intersect select * from A where
> B.x=A.x
> and A.y=B.y
> and A.z=B.z
> limit 100
>
> I need the most efficient method possible; my A tables have upward of 5
> Million records. The B table, btw, only has about 100 records.
>
> Any help will be most appreciated.
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To: pgsql-sql@postgresql.org
Cc: ken@kencorey.com, jdiehl@sandia.gov, pgsql-general@postgresql.org
Subject: Re: Help with query. (*)
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