Re: select by groups

Martin Marques <martin(at)bugs(dot)unl(dot)edu(dot)ar> writes:

> I have a table with names of people, email address, etc, and an identifier
> that tells me which group they are in (could be a 1, 2, or 3 person group).
> Is it posible to make a query that would give me the name of the persons of
> each group in one row? Or do I have to do PL?

Use GROUP BY with an aggregator that concatenate the names. The
aggregator may be implemented in plpgsql, for instance:

CREATE OR REPLACE FUNCTION concat (text, text) RETURNS text
AS 'select case when $1 = '''' then $2 else ($1 || '', '' || $2) end'
LANGUAGE sql;

CREATE AGGREGATE concat (
BASETYPE = text,
SFUNC = public.concat,
STYPE = text,
INITCOND = ''
);

Regards,
Manuel.