Re: trivial sql help

On Thu, Oct 10, 2002 at 09:14:41AM -0700, Stephan Szabo wrote:
>
> On Thu, 10 Oct 2002, Patrick Welche wrote:
>
> > update rawrequest
> >    set cid=(select pc.c
> >               from pers_comp as pc
> >              where pc.p=pid
> >              group by pc.c
> >             having count(pc.c)=1
> >            )
> >  where pr
> > ;
> >
> > ERROR:  More than one tuple returned by a subselect used as an expression.
> >
> > pid, pc.p, pc.c, cid are all integers. pc just has 2 columns p and c.
> >
> > I thought putting the count()=1 in there would force a single tuple..
>
> No, that'll limit you only to groups having a count of 1.  It'll still
> give multiple groups.  You could probably use limit to get 1 row, but
> what's the actual behavior you want the update to have?

pers_comp relates person to computer. 99% of students have 1 computer =>
only one pers_comp(p,c) entry. I just wanted to fill in the computer's id
into the request of a given person for the simple case.

Anyway, I was just having brain failure.. as you have all happily explained
away the error message, I'll try again..

Cheers,

Patrick