MySql 语法速查

1. 启动服务

mysql -uroot -p

2. 显示所有数据库

show databases;

3. 创建数据库

create databases 数据库名称;

4. 切换数据库

use j2ee;

5. 显示所有表

show tables;

6. 显示表格信息

mysql> desc User;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id       | int(11)     | NO   | PRI | NULL    |       |
| username | varchar(30) | YES  |     | NULL    |       |
| password | varchar(10) | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

7. 增删查改表格

创建表

create table 表名（
列名1：列的类型
列名2：列的类型
列名3：列的类型
）
CREATE TABLE IF NOT EXISTS `runoob_tbl`(
   `runoob_id` INT UNSIGNED AUTO_INCREMENT,
   `runoob_title` VARCHAR(100) NOT NULL,
   `runoob_author` VARCHAR(40) NOT NULL,
   `submission_date` DATE,
   PRIMARY KEY ( `runoob_id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

mysql> create table Role(
    -> `role_id` int(3),
    -> `role_name` varchar(30),
    -> primary key(`role_id`));
Query OK, 0 rows affected (0.06 sec)

mysql> desc Role;
+-----------+-------------+------+-----+---------+-------+
| Field     | Type        | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| role_id   | int(3)      | NO   | PRI | NULL    |       |
| role_name | varchar(30) | YES  |     | NULL    |       |
+-----------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

增加一个属性

alter table 表名 add column 列名 类型；

补充说明——多对多关系

多对多连接

插入一条记录

insert into tablename(列名1，列名2.....列名n)
,(值1，值2.......值n)，
,(值1，值2.......值n)，
,(值1，值2.......值n);

insert into Role(role_id,role_name) values(001,'Teacher');

mysql> insert into Role(role_id,role_name) values(002,'Student'),(003,'Manager');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from role;                                                      
+---------+-----------+
| role_id | role_name |
+---------+-----------+
|       1 | Teacher   |
|       2 | Student   |
|       3 | Manager   |
+---------+-----------+
3 rows in set (0.00 sec)

删除一条记录

delete from attend_table where duty_day='2019-05-27';

清空表格

TRUNCATE TABLE table1