| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Stuart Rison <rison(at)biochemistry(dot)ucl(dot)ac(dot)uk> |
| Cc: | Moray McConnachie <moray(dot)mcconnachie(at)computing-services(dot)oxford(dot)ac(dot)uk>, pgsql-sql <pgsql-sql(at)postgreSQL(dot)org> |
| Subject: | Re: [SQL] DISTINCT & COUNT |
| Date: | 1999-11-26 18:19:27 |
| Message-ID: | 16209.943640367@sss.pgh.pa.us |
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| Lists: | pgsql-sql |
Stuart Rison <rison(at)biochemistry(dot)ucl(dot)ac(dot)uk> writes:
> You can however do:
> SELECT DISTINCT c.cid
> FROM a,b,c
> WHERE a.aid=b.aid
> AND a.somefield=1 and a.otherfield=2
> AND c.cid=a.cid;
> and if your are using a interface (e.g. DBI::DBD::Pg) then you can get
> the number of tuples returned...
Or do the SELECT into a temp table, followed by fetching count(*) on the
temp table. Ugly, but avoids transferring what might be a lot of rows
to the frontend.
DISTINCT within aggregate functions is on the TODO list, but I don't
know when it will happen.
regards, tom lane
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