所以，我有一个订阅表:id-int(11)(WithPrimaryKey)user_id-int(11)group_id-int(11)role-int(11)pending-tinyint(1)created_at-datetimeupdated_at-datetime我经常查询用户是否有类似这样的访问权限:SELECT*FROM`subscriptions`WHERE(group_id=1ANDuser_id=2ANDpending=0)LIMIT1我想知道在subscriptions(group_id,user_id,pending)上添加唯一索引在这种情况下会有所帮助还是有阻碍