"David E. Wheeler" <david@kineticode.com> writes:
> Because it's an aggregate that cocatenates values. It's not an
> aggregate that lists things. I also like concat_agg better than
> string_agg because it's not limited to acting on strings.
But what it *produces* is a string. For comparison, the
SQL-standard-specified array_agg produces arrays, but what it
acts on isn't an array.
regards, tom lane