mysql 查询用法

#去重复查询DISTINCT

mysql> select * from student;

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

| uid | name | age |

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

| 3 | hong | 30 |

| 2 | aaa | 20 |

| 1 | bbb | 26 |

| 4 | ccc | 20 |

| 4 | ccc | 30 |

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

5 rows in set (0.00 sec)

mysql> select distinct name from student;

+------+

| name |

+------+

| hong |

| aaa |

| bbb |

| ccc |

+------+

4 rows in set (0.00 sec)

#使用AND和OR进行多条件查询

mysql> select * from student where uid=5 and age<30;

Empty set (0.00 sec)

mysql> select * from student where age>30;

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

| uid | name | age |

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

| 5 | eee | 31 |

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

1 row in set (0.00 sec)

mysql> select * from student where uid<5 or age>30;

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

| uid | name | age |

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

| 2 | aaa | 20 |

| 1 | bbb | 26 |

| 4 | ccc | 20 |

| 3 | ccc | 30 |

| 5 | eee | 31 |

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

5 rows in set (0.00 sec)

#要加括号

mysql> select * from student where name='aaa' and (age=20 or age=30);

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

| uid | name | age |

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

| 2 | aaa | 20 |

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

1 row in set (0.00 sec)