select시 순서에대한 값을 구하고자 할경우 ranking

mysql> set@a = 0;
Query OK, 0 rows affected (0.01 sec)
mysql> select @a := @a + 1 as rank, num,id from member where order by num desc;
+------+-----+--------+
| rank  | num | id        |
+------+-----+--------+
|    1    | 9     | bbbb    |
|    2    | 5     | abbb    |
|    3    | 3     | cbbb    |
+------+-----+--------+
3 rows in set (0.00 sec)