diff --git a/db/app_uoj233.sql b/db/app_uoj233.sql
index 3ae2d3a..c33a8ce 100644
--- a/db/app_uoj233.sql
+++ b/db/app_uoj233.sql
@@ -455,11 +455,10 @@ CREATE TABLE `groups` (
 /*!40101 SET @saved_cs_client     = @@character_set_client */;
 /*!40101 SET character_set_client = utf8mb4 */;
 CREATE TABLE `groups_assignments` (
-  `id` int(11) NOT NULL AUTO_INCREMENT,
-  `list_id` int(11) NOT NULL,
   `group_id` int(11) NOT NULL,
+  `list_id` int(11) NOT NULL,
   `end_time` datetime NOT NULL,
-  PRIMARY KEY (`id`)
+  PRIMARY KEY (`group_id`, `list_id`)
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4;
 /*!40101 SET character_set_client = @saved_cs_client */;
 
diff --git a/web/app/libs/uoj-query-lib.php b/web/app/libs/uoj-query-lib.php
index e6d69ad..330a348 100644
--- a/web/app/libs/uoj-query-lib.php
+++ b/web/app/libs/uoj-query-lib.php
@@ -146,10 +146,10 @@ function queryGroupCurrentAC($group_id) {
 	return DB::selectAll("select a.problem_id as problem_id, a.submitter as submitter, a.submission_id as submission_id, b.submit_time as submit_time, d.title as problem_title, b.submit_time as submit_time, e.realname as realname from best_ac_submissions a inner join submissions b on (a.submission_id = b.id) inner join groups_users c on (a.submitter = c.username and c.group_id = $group_id) inner join problems d on (a.problem_id = d.id and d.is_hidden = 0) inner join user_info e on (a.submitter = e.username) where b.submit_time > addtime(now(), '-360:00:00') order by b.submit_time desc limit 10", MYSQLI_ASSOC);
 }
 function queryGroupAssignments($group_id) {
-	return DB::selectAll("select a.id as id, a.list_id as list_id, a.end_time as end_time, b.title from groups_assignments a left join lists b on a.list_id = b.id where a.group_id = $group_id order by a.end_time asc", MYSQLI_ASSOC);
+	return DB::selectAll("select a.list_id as list_id, a.end_time as end_time, b.title from groups_assignments a left join lists b on a.list_id = b.id where a.group_id = $group_id order by a.end_time asc", MYSQLI_ASSOC);
 }
 function queryGroupActiveAssignments($group_id) {
-	return DB::selectAll("select a.id as id, a.group_id as group_id, a.list_id as list_id, a.end_time as end_time, b.title from groups_assignments a left join lists b on a.list_id = b.id where a.group_id = $group_id and a.end_time >= addtime(now(), '-168:00:00') order by a.end_time asc", MYSQLI_ASSOC);
+	return DB::selectAll("select a.group_id as group_id, a.list_id as list_id, a.end_time as end_time, b.title from groups_assignments a left join lists b on a.list_id = b.id where a.group_id = $group_id and a.end_time >= addtime(now(), '-168:00:00') order by a.end_time asc", MYSQLI_ASSOC);
 }
 function queryAssignmentByGroupListID($group_id, $list_id) {
 	return DB::selectFirst("select * from groups_assignments where list_id='$list_id' and group_id='$group_id'", MYSQLI_ASSOC);
diff --git a/web/app/upgrade/8_group_v2/down.sql b/web/app/upgrade/8_group_v2/down.sql
index 8008d9d..b77c2f6 100644
--- a/web/app/upgrade/8_group_v2/down.sql
+++ b/web/app/upgrade/8_group_v2/down.sql
@@ -1,4 +1,6 @@
 RENAME TABLE groups_assignments TO assignments;
+ALTER TABLE `assignments` ADD COLUMN `id` int(11) NOT NULL AUTO_INCREMENT;
+ALTER TABLE `assignments` DROP PRIMARY KEY, ADD PRIMARY KEY (`id`);
 ALTER TABLE `assignments` ADD COLUMN `create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP;
 ALTER TABLE `assignments` CHANGE COLUMN `end_time` `deadline` datetime NOT NULL;
 ALTER TABLE `countdowns` CHANGE COLUMN `end_time` `endtime` datetime NOT NULL;
diff --git a/web/app/upgrade/8_group_v2/up.sql b/web/app/upgrade/8_group_v2/up.sql
index 347d0b1..8dea4cc 100644
--- a/web/app/upgrade/8_group_v2/up.sql
+++ b/web/app/upgrade/8_group_v2/up.sql
@@ -1,4 +1,6 @@
 RENAME TABLE assignments TO groups_assignments;
+ALTER TABLE `assignments` DROP PRIMARY KEY, ADD PRIMARY KEY (`group_id`, `list_id`);
+ALTER TABLE `assignments` DROP COLUMN `id`;
 ALTER TABLE `groups_assignments` DROP COLUMN `create_time`;
 ALTER TABLE `groups_assignments` CHANGE COLUMN `deadline` `end_time` datetime NOT NULL;
 ALTER TABLE `countdowns` CHANGE COLUMN `endtime` `end_time` datetime NOT NULL;