Re: UNION DISTINCT in doc

2010/10/15 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> writes:
>> UNION DISTINCT is nothing more than UNION itself, but gram.y
>> definitely accept it and the SQL standard describes it as well. Should
>> we add DISTINCT to docs?
>
> I think it'd be hard to describe without confusing people, because
> while DISTINCT is a noise word there, it's definitely not a noise
> word after SELECT.  And the way that the reference pages are laid
> out, it's hard to connect different descriptions of the same
> keyword to different usages.  If you can think of a non-forced
> way of describing this, fine.  But I don't have a problem with
> leaving it as an undocumented standards-compliance nit.

I thought adding DISTINCT next to ALL is enough like

select_statement UNION [ ALL | DISTINCT ] select_statement

and say "UNION DISTINCT is identical to UNION only" or something. That
sounds not so confusing with DISTINCT clause description.

Regards,

--
Hitoshi Harada