Mysql中对表字段的增删改查

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Mysql中对表字段的增删改查

来源: 作者: 时间:2016-02-05 10:56 【

Mysql中对表字段的增删改查mysql中对表字段的增加,修改(修改类型),删除,排序1 建立一个new 表,表中字段:学号,姓名,年龄。mysql create table new (ne_id int(10),ne_name varchar(20),ne_age i
Mysql中对表字段的增删改查
 
中对表字段的增加,修改(修改类型),删除,排序
 
1.建立一个new 表,表中字段:学号,姓名,年龄。

mysql> create table new (ne_id int(10),ne_name varchar(20),ne_age int(12));

Query OK, 0 rows affected (0.97 sec)

2.表的结构图

mysql> desc new;

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

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

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

| ne_id   | int(10)     | YES  |     | NULL    |       |

| ne_name | varchar(20) | YES  |     | NULL    |       |

| ne_age  | int(12)     | YES  |     | NULL    |       |

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

 rows in set (0.01 sec)

3.向new 表中添加一个地址

mysql> alter table new add ne_address varchar(20);

Query OK, 0 rows affected (1.28 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> desc new;

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

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

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

| ne_id      | int(10)     | YES  |     | NULL    |       |

| ne_name    | varchar(20) | YES  |     | NULL    |       |

| ne_age     | int(12)     | YES  |     | NULL    |       |

| ne_address | varchar(20) | YES  |     | NULL    |       |

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

rows in set (0.00 sec)

4.将字段名ne_id 改名为 ne_nor

mysql> alter table new change ne_id ne_nor int(10);

Query OK, 0 rows affected (0.22 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> desc new;

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

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

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

| ne_nor     | int(10)     | YES  |     | NULL    |       |

| ne_name    | varchar(20) | YES  |     | NULL    |       |

| ne_age     | int(12)     | YES  |     | NULL    |       |

| ne_address | varchar(20) | YES  |     | NULL    |       |

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

4 rows in set (0.00 sec)

5.删除字段ne_nor 

mysql> alter table new drop ne_nor;

Query OK, 0 rows affected (1.04 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> desc new;

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

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

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

| ne_name    | varchar(20) | YES  |     | NULL    |       |

| ne_age     | int(12)     | YES  |     | NULL    |       |

| ne_address | varchar(20) | YES  |     | NULL    |       |

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

3 rows in set (0.00 sec)

6.修改字段类型:将ne_age 的 int 改为 varchar

mysql> alter table new modify ne_age varchar(20);

Query OK, 0 rows affected (1.34 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> desc new;

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

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

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

| ne_name    | varchar(20) | YES  |     | NULL    |       |

| ne_age     | varchar(20) | YES  |     | NULL    |       |

| ne_address | varchar(20) | YES  |     | NULL    |       |

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

3 rows in set (0.01 sec)

7.排序

mysql> alter table new modify ne_age varchar(20) after ne_address;

Query OK, 0 rows affected (0.98 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> desc new;

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

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

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

| ne_name    | varchar(20) | YES  |     | NULL    |       |

| ne_address | varchar(20) | YES  |     | NULL    |       |

| ne_age     | varchar(20) | YES  |     | NULL    |       |

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

3 rows in set (0.00 sec)

 


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