diff --git a/sql/mysql/upgrade/3.1.6.3/groups-integrity.sql b/sql/mysql/upgrade/3.1.6.3/groups-integrity.sql
index e7425d7..74ce68a 100644
--- a/sql/mysql/upgrade/3.1.6.3/groups-integrity.sql
+++ b/sql/mysql/upgrade/3.1.6.3/groups-integrity.sql
@@ -1,7 +1,36 @@
+-- PREPARE FOR ADDING CONSTRAINTS ON `groups_groups_link`
+
+-- parent_group_id
+
+DELETE FROM `groups_groups_link` as gg USING `groups_groups_link` as gg, groups_lookup  
+	WHERE not exists(select 1 from `groups_lookup` as g where gg.parent_group_id = g.id);
+
+-- member_group_id
+
+DELETE FROM `groups_groups_link` as gg USING `groups_groups_link` as gg, groups_lookup  
+	WHERE not exists(select 1 from `groups_lookup` as g where gg.member_group_id = g.id);
+
+-- ADD CONSTRAINT
+
 ALTER TABLE `groups_groups_link`
   ADD CONSTRAINT `groups_groups_link_ibfk_1` FOREIGN KEY (`parent_group_id`) REFERENCES `groups_lookup` (`id`) ON DELETE CASCADE,
   ADD CONSTRAINT `groups_groups_link_ibfk_2` FOREIGN KEY (`member_group_id`) REFERENCES `groups_lookup` (`id`) ON DELETE CASCADE;
-  
+
+-- PREPARE FOR ADDING CONSTRAINTS ON `users_groups_link`
+
+-- group_id
+
+DELETE FROM `users_groups_link` as ug USING `users_groups_link` as ug, groups_lookup
+	WHERE not exists(select 1 from `groups_lookup` as g where ug.group_id = g.id);
+
+-- user_id
+
+DELETE FROM `users_groups_link` as ug USING `users_groups_link` as ug, users
+	WHERE not exists(select 1 from `users` as u where ug.user_id = u.id);
+
+-- ADD CONSTRAINT
+
 ALTER TABLE `users_groups_link`
   ADD CONSTRAINT `users_groups_link_ibfk_1` FOREIGN KEY (`group_id`) REFERENCES `groups_lookup` (`id`) ON DELETE CASCADE,
   ADD CONSTRAINT `users_groups_link_ibfk_2` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE;  
+