DELETE FROM partitur WHERE EXISTS (SELECT * FROM partitur AS ss_partitur
WHERE ss_partitur.userid=partitur.userid AND ss_partitur.ts>partitur.ts);
Seems like it should seems like it should delete all old values (however I
have not tested it)
- Stuart
> -----Original Message-----
> From: Haller Christoph [SMTP:ch@rodos.fzk.de]
> Sent: Tuesday, October 16, 2001 5:45 PM
> To: pgsql-sql@postgresql.org
> Subject: Deleting obsolete values
>
> This may look familiar to you - it was on the list last month.
> Consider the following table
> create table partitur
> (userid text, val integer, ts timestamp DEFAULT NOW() );
> Do some inserts
> insert into partitur values('Bart', 1440);
> insert into partitur values('Lisa', 1024);
> insert into partitur values('Bart', 7616);
> insert into partitur values('Lisa', 3760);
> insert into partitur values('Bart', 3760);
> insert into partitur values('Lisa', 7616);
> To retrieve the latest values (meaning the last ones inserted)
> Tom Lane wrote
> >This is what SELECT DISTINCT ON was invented for. I don't know any
> >comparably easy way to do it in standard SQL, but with DISTINCT ON
> >it's not hard:
> >SELECT DISTINCT ON (userid) userid, val, ts FROM partitur
> >ORDER BY userid, ts DESC;
>
> My question now is
> Is there a way to delete all rows the select statement did not
> bring up?
> After that *unknown* delete statement
> select userid, val, ts from partitur ;
> should show exactly the same as the SELECT DISTINCT ON (userid) ...
> did before.
>
> Regards, Christoph
