几个sql语句中的case使用

表结构

+-------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | | |

| name | varchar(20) | YES | | NULL | |

| sex | char(1) | YES | | NULL | |

| addr | varchar(50) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

1. select id, name

,(case sex when 'm' then '男' when 'f' then '女' else '其他' end) "性别"

from stu;

结果:

+------+----------+------+

| id | name | 性别 |

+------+----------+------+

| 1101 | andylin | 男 |

| 1102 | congfeng | 男 |

| 1103 | lihong | 女 |

+------+----------+------+

2. select id, name

, (case sex when 'm' then '男' end) "male"

, (case sex when 'f' then '女' end) "female"

from stu;

结果:

+------+----------+------+--------+

| id | name | male | female |

+------+----------+------+--------+

| 1101 | andylin | 男 | NULL |

| 1102 | congfeng | 男 | NULL |

| 1103 | lihong | NULL | 女 |

+------+----------+------+--------+