From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Mike Benoit <ipso(at)snappymail(dot)ca>, Michael Glaesemann <grzm(at)seespotcode(dot)net>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: ORDER BY col is NULL in UNION causes error? |
Date: | 2007-01-11 20:04:25 |
Message-ID: | 200701112004.l0BK4Pa27274@momjian.us |
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Lists: | pgsql-general |
Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > Well, it can be an expression _if_ the expression _matches_ an existing
> > UNION column.
>
> You're mistaken. It has to be *an output column name*. Not anything else.
Yea, I was thinking of this:
SELECT *, state IS NULL AS state_is_null
FROM income_tax_rate_us
UNION
SELECT *, state IS NULL AS state_is_null
FROM income_tax_rate_us
ORDER BY state_is_null
Here the column result is an expression, and you reference that.
Updated wording:
test=> select * from test union select * from test order by x is null;
ERROR: A UNION/INTERSECT/EXCEPT ORDER BY cannot use expressions or functions, only result column names
--
Bruce Momjian bruce(at)momjian(dot)us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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