[MySQL] student table - 22=1학년, 23=2학년, 24=3학년, 25=4학년으로 하는 grade속성 추가

mysql> update student set grade = 1 where age = 22;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

ysql> update student set grade = 3 where age = 24;
Query OK, 2 rows affected (0.00 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> update student set grade = 2 where age = 23;
Query OK, 2 rows affected (0.00 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> update student set grade = 4 where age = 25;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from student;
+------+--------+------+---------+----------+-------+-------+
| num  | name   | age  | address | major    | score | grade |
+------+--------+------+---------+----------+-------+-------+
| 1111 | 홍길동 |   24 | seoul   | computer |    89 |     3 |
| 2222 | 강길순 |   25 | seoul   | English  |    87 |     4 |
| 3333 | 이순신 |   23 | Inchen  | English  |    57 |     2 |
| 5555 | 유관순 |   22 | suwon   | Computer |    97 |     1 |
| 6666 | 다래냥 |    2 | Inchen  | computer |   100 |  NULL |
| 7777 | 다래옹 |   24 | Inchen  | English  |    20 |     3 |
| 8888 | 다래잉 |   27 | Inchen  | computer |    80 |  NULL |
| 9999 | 다래뇽 |   23 | seoul   | computer |    70 |     2 |
+------+--------+------+---------+----------+-------+-------+
8 rows in set (0.00 sec)