| From: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
|---|---|
| To: | "Marko Rihtar *EXTERN*" <rihtar(dot)marko(at)gmail(dot)com>, "pgsql-admin(at)postgresql(dot)org" <pgsql-admin(at)postgresql(dot)org> |
| Subject: | Re: Avoid casting NULLs in UNION... |
| Date: | 2013-02-01 10:26:07 |
| Message-ID: | A737B7A37273E048B164557ADEF4A58B057AE08C@ntex2010a.host.magwien.gv.at |
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| Lists: | pgsql-admin |
Marko Rihtar wrote:
> maybe you can help me with this issue.
> Here is an example
>
> SELECT NULL::integer
> UNION ALL
> SELECT NULL
> UNION ALL
> SELECT 123
>
> For this sql to work i have to cast NULL to integer.
> I was wondering if there exists some configuration parameter at database level that can be used to
> avoid this need for explicit casting?
Not that I know of.
The behaviour is well defined and documented, see
http://www.postgresql.org/docs/current/static/typeconv-union-case.html
The UNIONs are computed left to right,
and the data type in the first UNION resolves to "text"
according to rule 2 of the page given above.
You can reorder the UNIONs or use parentheses.
Yours,
Laurenz Albe
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