版权声明：17602128911 https://blog.csdn.net/bus_lupe/article/details/88230700
主键：非空且唯一 not null unique
查看表
mysql> show tables;
+----------------+
| Tables_in_bibi |
+----------------+
| employee |
| runoob_tbl |
+----------------+
2 rows in set (0.00 sec)
查看某张表
mysql> desc employee;
+-------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
+-------+------------------+------+-----+---------+----------------+
1 row in set (0.01 sec)
查看创建表的信息
mysql> show create table employee;
+----------+--------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+----------+--------------------------------------------------------------------------------------------------------------------------------------+
| employee | CREATE TABLE `employee` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+----------+--------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
修改表结构
添加一个字段
mysql> alter table employee add name varchar(25);
Query OK, 0 rows affected (0.07 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc employee;
+-------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(25) | YES | | NULL | |
+-------+------------------+------+-----+---------+----------------+
2 rows in set (0.01 sec)
添加多个字段
mysql> alter table employee add A int,
-> add B varchar(20);
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc employee;
+------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(25) | YES | | NULL | |
| gender | tinyint(1) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
| department | varchar(20) | YES | | NULL | |
| salary | double(7,2) | YES | | NULL | |
| is_married | tinyint(1) | YES | | NULL | |
| entry_date | date | NO | | NULL | |
| A | int(11) | YES | | NULL | |
| B | varchar(20) | YES | | NULL | |
+------------+------------------+------+-----+---------+----------------+
10 rows in set (0.01 sec)
删除一个字段
mysql> alter table employee drop A;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
删除多个字段
mysql> alter table employee drop B,
-> drop entry_date;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
修改一列类型
mysql> alter table employee modify age smallint not null default 18 after id;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc employee;
+------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| age | smallint(6) | NO | | 18 | |
| name | varchar(25) | YES | | NULL | |
| gender | tinyint(1) | YES | | NULL | |
| department | varchar(20) | YES | | NULL | |
| salary | double(7,2) | YES | | NULL | |
| is_married | tinyint(1) | YES | | NULL | |
+------------+------------------+------+-----+---------+----------------+
7 rows in set (0.01 sec)
修改列名
mysql> alter table employee change department depart varchar(20) after salary;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc employee;
+------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| age | smallint(6) | NO | | 18 | |
| name | varchar(25) | YES | | NULL | |
| gender | tinyint(1) | YES | | NULL | |
| salary | double(7,2) | YES | | NULL | |
| depart | varchar(20) | YES | | NULL | |
| is_married | tinyint(1) | YES | | NULL | |
+------------+------------------+------+-----+---------+----------------+
7 rows in set (0.01 sec)
修改表名
mysql> rename table employee to emp;
Query OK, 0 rows affected (0.01 sec)
mysql> show tables;
+----------------+
| Tables_in_bibi |
+----------------+
| emp |
| runoob_tbl |
+----------------+
2 rows in set (0.00 sec)
删除表
drop table tab_name;