mysql> create table t (i1 int, i2 int);
Query OK, 0 rows affected (0.01 sec)
mysql> insert t set i1 = 1, i2 = 5;
Query OK, 1 row affected (0.00 sec)
mysql> insert t set i1 = 2, i2 = 5;
Query OK, 1 row affected (0.00 sec)
mysql> select * from t order by i2/i1;
+------+------+
| i1 | i2 |
+------+------+
| 2 | 5 |
| 1 | 5 |
+------+------+
2 rows in set (0.00 sec)
mysql> select * from t order by i2/i1 desc;
+------+------+
| i1 | i2 |
+------+------+
| 1 | 5 |
| 2 | 5 |
+------+------+
2 rows in set (0.00 sec)