mysql> select * from test;
+----+--------+
| id | prefix |
+----+--------+
| 1 | 1 |
| 2 | 12 |
| 3 | 123 |
| 4 | 1234 |
| 5 | 12345 |
+----+--------+
5 rows in set (0.00 sec)mysql> select * from test where left('1288977324324212', length(prefix)) = prefix order by prefix desc limit 1;
+----+--------+
| id | prefix |
+----+--------+
| 2 | 12 |
+----+--------+
1 row in set (0.00 sec)
mysql> select * from test where left('12388977324324212', length(prefix)) = prefix order by prefix desc limit 1;
+----+--------+
| id | prefix |
+----+--------+
| 3 | 123 |
+----+--------+
1 row in set (0.00 sec)
mysql> select * from test where left('123488977324324212', length(prefix)) = prefix order by prefix desc limit 1;
+----+--------+
| id | prefix |
+----+--------+
| 4 | 1234 |
+----+--------+
1 row in set (0.00 sec)