sql query: unique users per forum?

[Sculli]

What I would like to do is to determine how many unique users posted to a forum. Unfortunately I have no idea about SQL in the first place.

I imagine it could work like this:

select all posts made in forum id 81 from posts_table
select user-id of all posters who made those posts
??? some sort of unique user-id query ???
display the number of unique users

Any help will be greatly appreciated.

[Paul M]

Try;

SELECT COUNT(post.dateline) AS count
FROM post 
LEFT JOIN thread USING (threadid)
WHERE thread.forumid = 81
GROUP BY post.username

[Sculli]

Awesome, worked like a charm, thank you ever so much.