Re: update only if single row - Mailing list pgsql-sql

Frank,

My apologies. You are right.
I read "if a single email is selected" and not
"if a single row is selected," like it says.

A function seems like the only logical place to go.

Just for the curiosity, though, here is a set of two queries which
handle the job:

SELECT max(email) as email into temp dummy from contact where email ~* 'rvro' having count(*) = 1;
UPDATE contact set bounce = 1 where email in (select email from dummy);

If you were able to use the first query as a subquery, then it would be just
one query. I don't see how to do that, though.


Troy




>
> Tony:
>
> No it is NOT supposed to update multiple rows.  Please re-read the
> requirements.
>
> >Can I combine this into a single SQL statement with the following
> >requirements:
> >1) the update is only performed if a single row is selected
> >2) I only enter the selection string ('rvro' in this case) once in the
> >command?
>
> The SQL statement should update the row with email address matching pattern
> ~* 'rvro' ONLY if a single row matches that pattern.  If multiple rows
> match the pattern, the update should NOT be performed.
>
> Frank
>
>
> At 03:42 PM 4/07/00 -0700, you wrote:
> >It is supposed to update multiple rows.
> >
> >It is supposed to update all rows which have an email
> >address matching the pattern ~* 'rvro', except rows
> >where there are other rows with the same email address.
> >
> >Troy
> >
> >> Except for one minor detail.  It updates multiple rows!
> >>
> >> At 02:39 AM 4/07/00 -0700, you wrote:
> >> >Excellent solution.
> >> >
> >> >You can use oid as the unique attribute.
> >> >
> >> > UPDATE contact SET bounce = 1 WHERE email ~* 'rvro' AND email NOT IN
> >> >  (SELECT c1.email FROM contact c1, contact c2
> >> >   WHERE c1.oid != c2.oid AND c1.email = c2.email);
> >> >
> >> >Troy
> >> >>
> >> >> FB> select * from contact where email ~* 'rvro';
> >> >> FB> if I get a single row in the result then I enter:
> >> >> FB> update contact set bounce=1 where  email ~* 'rvro';
> >> >>
> >> >> FB> Can I combine this into a single SQL statement with the following
> >> >> FB> requirements:
> >> >> FB> 1) the update is only performed if a single row is selected
> >> >> FB> 2) I only enter the selection string ('rvro' in this case) once
> in the
> >> >> FB> command?
> >> >>
> >> >> Assume that pk is PRIMARY KEY (or UNIQUE attribute) of relation contact.
> >> >>
> >> >> UPDATE contact SET bounce = 1 WHERE email ~* 'rvro' AND NOT email IN
> >> >>  (SELECT c1.email FROM contact c1, contact c2
> >> >>   WHERE c1.pk != c2.pk AND c1.email = c2.email);
> >> >>
> >> >> LPK Station                            mailto:kl@84105.aanet.ru
>