Re: [GENERAL] Problem with a GROUP BY clause

--- Herouth Maoz <herouth@oumail.openu.ac.il> wrote:
> At 03:52 +0300 on 01/08/1999, Mark Dalphin wrote:
>
>
> > There is no row, yet Postgresql reports there is
> "one" which it returns as
> > empty.  This also makes the Perl DBI::DBD
> interface unhappy. It seems to
> >return
> > an undefined value which can't even be tested with
> "if(! defined $value)"!
> >
> > Unless I really misunderstand "GROUP BY", I think
> this is a bug.
>
> We had this discussion in the past and I think you
> are right in saying that
> under "GROUP BY", this behaviour is a bug. However,
> it is not really that
> hard to handle. It merely returns a row with NULL
> values all over. Test for
> NULL in the same way you test for NULL in any field
> that may have NULL
> values. You can be sure that if a valid grouping was
> returned, neither
> field will be null.
>
> Herouth

Of course, one way to get around the bug until it is
fixed (although I don't see it on the TODO...) is to
issue the query like this:

select field1, max(field2) from table1
group by field1 having max(field2) is not null;

Hope that helps,

Mike Mascari (mascarim@yahoo.com)

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