mysql> select grplist from ringgroups where grpnum='612';
+-------------------------+
| grplist                 |
+-------------------------+
| 428-438-441-442-443-448 |
+-------------------------+
1 row in set (0.00 sec)

mysql> select extension, name from users where extension in (428,438,441,442,442,448);
+-----------+--------------------------------------------+
| extension | name                                       |
+-----------+--------------------------------------------+
| 438       | 438 GORliniya                              |
| 441       | Kuznetsova Anna  441 Gorliniya             |
| 442       | Vorgunova Anna  442 Gorliniya              |
| 428       | Gusevskaya Olesya GORliniya  428           |
| 448       | Beregovets Nataliya 448 Ur otdel Gorliniya |
+-----------+--------------------------------------------+
5 rows in set (0.00 sec)