From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Tamsin" <tg_mail(at)bryncadfan(dot)co(dot)uk> |
Cc: | "Postgres General" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: union query |
Date: | 2001-01-12 15:41:19 |
Message-ID: | 15863.979314079@sss.pgh.pa.us |
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Lists: | pgsql-general |
"Tamsin" <tg_mail(at)bryncadfan(dot)co(dot)uk> writes:
> select 'other' union select description from address;
> ERROR: Unable to transform varchar to unknown
> Each UNION | EXCEPT | INTERSECT clause must have compatible target
> types
The behavior in 7.0.* and before (as far back as I recall) has been that
the first select determines the output type of the union, so the above
fails, but reversing it works. 7.1 is a little smarter about
unknown-type literals, so it accepts both of your cases, but it will
still do the Wrong Thing for examples like select int4 union select int8.
> I just wondered
> if the order of the selects in a union should matter?
It shouldn't, really, but without a complete type promotion hierarchy
we have a hard time doing anything intelligent with arbitrary pairs of
types.
regards, tom lane
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