using or_where() on same field

[eluser]blorriman[/eluser]
Well, this is what I'm getting, and it seems to work for members who have not resigned (resign_date IS NULL) as well as for members who resigned after the start_date.

Code:

SELECT * FROM (`members`)
JOIN `groups_members` ON `groups_members`.`member_id` = `members`.`user_id`
WHERE `groups_members`.`group_id` = '81'
AND `groups_members`.`join_date` <= '2010-05-08'
OR `groups_members`.`resign_date` IS NULL
AND `groups_members`.`resign_date` >= '2010-04-28'
ORDER BY `last_name` asc