2010/8/4 Thom Brown <t...@linux.com>: > On 4 August 2010 14:24, Pavel Stehule <pavel.steh...@gmail.com> wrote: >> 2010/8/4 Thom Brown <t...@linux.com>: >>> On 4 August 2010 14:04, Robert Haas <robertmh...@gmail.com> wrote: >>>> On Wed, Aug 4, 2010 at 6:03 AM, Thom Brown <t...@linux.com> wrote: >>>>> Actually, this rings a bell. I think this may have been raised >>>>> before, something to do with the delimiter being accepted as one of >>>>> the order by values. If this isn't really a bug, could someone >>>>> mention it in the docs somewhere? >>>> >>>> Oh, yeah. I guess you need this: >>>> >>>> select thing, string_agg(stuff, ',' order by stuff) from agg_test >>>> group by thing; >>>> >>>> Rather than this: >>>> >>>> select thing, string_agg(stuff order by stuff, ',') from agg_test >>>> group by thing; >>>> >>>> It's all kinds of not obvious to me what the second one is supposed to >>>> mean, but I remember this was discussed before. Perhaps we need a >>>> <note> somewhere about multi-argument aggregates. >>>> >>> >>> Yes, that works with the order clause. That's really weird! It looks >>> like part of the delimiter parameter, and that's undocumented, or at >>> least impossible to gleen from the documentation. >>> >>> This should be clarified as it looks like having ORDER BY *or* a >>> delimiter is supported, but not both. It's horribly unintuitive! >>> This is one of the very few cases where MySQL's version actually makes >>> more sense. >> >> this goes from ANSI SQL standard :( - I agree, this isn't intuitive >> and pg can do better diagnostic now. But it has a sense. ORDER BY >> hasn't sense for one parameter - only for complete function, so is >> wrong to write ORDER BY over a some interesting parameter >> >> Regards >> >> Pavel Stehule >> > > So really, should the documentation be changed from: > > string_agg(expression [, delimiter ] ) > > to > > string_agg(expression [, delimiter ] [ GROUP BY expression [, ...] ] )
This syntax is available for all aggregate functions - this feature isn't specific for string_agg but there can be more descriptive example. Regards Pavel > > ? > > -- > Thom Brown > Registered Linux user: #516935 > -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
