Social Engine

# 
SELECT `user_id` FROM `engine4_invites` GROUP BY `user_id`
 
# User 1 invited ...
SELECT users.`user_id`,`displayname`, `email` FROM `engine4_invites` invites 
	JOIN `engine4_users` users ON invites.`new_user_id` = users.`user_id` 
	WHERE invites.`user_id` = 1
 
# User 1 was invited by ...
SELECT users.`user_id`,`displayname`, `email` FROM `engine4_invites` invites 
	JOIN `engine4_users` users ON invites.`user_id` = users.`user_id` 
	WHERE `new_user_id` = 1
 
# Never registered
SELECT users.`user_id` 'Invited by (id)',`displayname` 'Invited by (name)', `recipient`, `code` FROM `engine4_invites` invites 
	JOIN `engine4_users` users ON invites.`user_id` = users.`user_id` 
	WHERE `new_user_id` = 0