Delete from partitur where userid NOT IN (SELECT DISTINCT ON (userid)
userid, val, ts FROM partitur)
"Haller Christoph" <ch@rodos.fzk.de> wrote in message
news:200110161445.QAA11833@rodos...
> 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
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
> (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)
