ALTER TABLE core_group_member ADD COLUMN user_id int(11) NOT NULL default 0;
+ALTER TABLE core_group_member ADD INDEX lookup_user_id (user_id);
--- remove duplicates...
+-- remove duplicates... (hopefully only one duplicate.. failes if > 2...)
delete from core_group_member where id in (
select mid FROM (
select
group_id,user_id
having n > 1
) s
-)
+);
ALTER TABLE core_group_member ADD UNIQUE KEY unique_group_user (group_id,user_id);