Re: Field size become unlimited in union... - Mailing list pgsql-general

On 05/03/2016 04:28 AM, Durumdara wrote:
> Hello!
>
> As I experienced, PGSQL changes the result field sizes to unlimited
> varchar, when I passed different field size in same column of the union.
>
> SP.Key - varchar(100)
> SP.Value - varchar(200)
>
> Example:
>
>   select 'a', value from sp
>   union all
>   select key, value from sp
>
>
> The first field is not limited to 100, it's unlimited varchar() (= Text,
> Memo, CLOB).
>
> So PG don't use the maximal field size (100).
>
>
> If I did cast on the field to resize to 100, the result is limited
> correctly.
>
>
>   select cast('a' as varchar(100)), value from sp
>   union all
>   select key, value from sp
>
>
> Can I force somehow to PG use the maximal size?
>
> Or must I know and equalize all field sizes in union?
>
> Or must I use temporary tables and inserts to not get this problem?


See below for complete explanation:

http://www.postgresql.org/docs/9.5/static/typeconv-union-case.html

10.5. UNION, CASE, and Related Constructs

>
> Thanks
>
> Regards
>     dd
>
>


--
Adrian Klaver
adrian.klaver@aklaver.com