I am going to upgrade my database from version 4 to 5.
However I found some of my web application doesn't work on MySQL5

e.g following statement works in 4 but not 5

SELECT f.*, c.id as cat_id, c.position as cat_position, c.state as
cat_state, c.name as cat_name, c.description as cat_desc,
c.image, c.url, m.member_name as mod_name, m.member_id as
mod_id, m.is_group, m.group_id, m.group_name, m.mid
FROM ibf_forums f, ibf_categories c
LEFT JOIN ibf_moderators m ON (f.id=m.forum_id)
WHERE c.id=f.category
ORDER BY c.position, f.position

Error:
Unknown column 'f.id' in 'on clause'

The alias seem not working?
What should I do, I dont want to rewrite all my sql statement....

Thanks.

Jason