Many-to-one subquery

I have a problem that I have not been able to solve efficiently, and
I'm confident that it can be done in a single query.

I have a mailing list archive that I want to do some statistics on. It
would tremendously ease my work if I could extract such statistics for
each individual poster in one go. That would, of course, be quite
easy, if I could do a SELECT DISTINCT poster FROM maillist as a
subquery and use that as an argument. For instance, if I have a
function postpct(date, date, varchar(30)) that calculates the
percentage of posts that a certain poster ($3) is responsible in a
certain time interval ($1 to $2), then how do I go about feeding that
function all distinct poster entries? I've tried different things with
joins, but the bit that actually worked was horribly inefficient.

Martin

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