Re: help on a query

O CHRIS HOOVER έγραψε στις Oct 8, 2004 :

> Just curious, what is wrong with the first way of coding the solution?
> ------------------( Forwarded letter 1 follows )---------------------
> Date: Fri, 8 Oct 2004 08:44:23 +0400
> To: Thomas.F.O'Connell[tfo]@sitening.com.comp, mmurrain@dbdes.com.comp
> Cc: pgsql-sql@postgresql.org.comp
> From: sad@bankir.ru.comp
> Sender: pgsql-sql-owner+m19150@postgresql.org.comp
> Subject: Re: [SQL] help on a query
> 
> On Friday 08 October 2004 07:10, Thomas F.O'Connell wrote:
> > A query that should get the job done is:
> >
> > SELECT registration_id
> > FROM registrations r
> > WHERE NOT EXISTS (
> > 	SELECT 1
> > 	FROM receipts
> > 	WHERE registration_id = r.registration_id
> > );
> 
> Don't, PLEASE, don't !!!
> 
> drive this way :
> 
> SELECT r.registration_id
>  FROM registrations AS r
> LEFT OUTER JOIN receipts AS rec
>  ON rec.registration_id = r.registration_id
> WHERE rec.registration_id IS NULL;

Some one could add the same dont please dont, and advise:

select registration_id FROM registrations
where registration_id not in (select registration_id from receipts);

but its actually version/data dependent i suppose.


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-- 
-Achilleus