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Re: NULL value in subselect in UNION causes error

From: Jan Wieck <JanWieck(at)Yahoo(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: NULL value in subselect in UNION causes error
Date: 2007-01-26 20:46:50
Message-ID: 45BA68BA.2080204@Yahoo.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 1/26/2007 3:41 PM, Tom Lane wrote:
> Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
>> Checked it against HEAD and 8.2:
>> postgres=# select 1, 1, 1 union select * from (select 2, null, 2) two;
>> ERROR:  failed to find conversion function from "unknown" to integer
> 
> It's always done that.   The SQL spec would tell you that you have to
> cast the null to some specific type.  We allow untyped nulls in contexts
> where we can derive a type from reasonably nearby context, but an
> integer two levels up and over in another union arm isn't very nearby
> IMHO.  So I'm not particularly concerned about making this work ...

That explains. Thanks.


Jan

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