Richard, Andreas,
thank you very much for your solutions. I took a look on
both solutions, but I choosed Andreas's solution because
is shorter :)
So Andreas, would you please give some more explanations
on your solution? I didn't work with functions and aggregate till
now.
I don't understand how this comma_aggregate works. I can see that this
function it is defined with two arguments, but the aggredate it is called
with a single argument.
And what is LANGUAGE sql IMMUTABLE STRICT ?
CREATE FUNCTION comma_aggregate(text,text) RETURNS text AS '
SELECT CASE WHEN $1 <> '''' THEN $1 || '', '' || $2 ELSE $2 END; '
LANGUAGE sql IMMUTABLE STRICT;
CREATE AGGREGATE comma (basetype=text, sfunc=comma_aggregate, stype=text, initcond='' );
Best regards,
Loredana