mysql> create table test(c1 text, c2 text, c3 int, c4 int, c5 text);
Query OK, 0 rows affected (0.23 sec)

mysql> insert into test (c1,c2,c3,c4,c5) values ('id1','аб',2,3,'5,6');
Query OK, 1 row affected (0.06 sec)

mysql> insert into test (c1,c2,c3,c4,c5) values ('id2','аб',2,3,'8,9');
Query OK, 1 row affected (0.06 sec)

mysql> select * from test;
+------+------+------+------+------+
| c1   | c2   | c3   | c4   | c5   |
+------+------+------+------+------+
| id1  | аб   |    2 |    3 | 5,6  |
| id2  | аб   |    2 |    3 | 8,9  |
+------+------+------+------+------+
2 rows in set (0.00 sec)

mysql> select min(c1) as c1, c2, c3, c4, group_concat(c5) as c5
    -> from test
    -> group by c2, c3, c4
    -> ;
+------+------+------+------+---------+
| c1   | c2   | c3   | c4   | c5      |
+------+------+------+------+---------+
| id1  | аб   |    2 |    3 | 5,6,8,9 |
+------+------+------+------+---------+
1 row in set (0.14 sec)

group_concat(distinct c5)