一. 数据库操作
1. 查看数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| zmedu |
+--------------------+
5 rows in set
注意：
– MySQL数据库指令不区分大小写，操作真正的表和库的时候才区分大小写
– 任何命令都以；结束
2. 创建数据库
mysql> create database zmgaosh;
Query OK, 1 row affected
每创建一个数据库都会在data下创建同名的文件夹，一个数据库说到底就是个文件夹
查看数据库，发现zmgaosh已经创建好了；
3. 选择数据库
select database(); 查看当前在哪个库
use zmgaosh ; 切换到zmgaosh
mysql> select database();
+------------+
| database() |
+------------+
| zmedu |
+------------+
1 row in set
mysql> use zmgaosh;
Database changed
mysql> select database();
+------------+
| database() |
+------------+
| zmgaosh |
+------------+
1 row in set
mysql>
4. 删除数据库
drop 删除数据库命令
mysql> drop database zmgaosh;
Query OK, 0 rows affected
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| zmedu |
+--------------------+
5 rows in set
mysql>
注意： drop命令将删除指定数据库的所有的表，而且没有任何提示；如果你到data目录下查看，会发现没有zmgaosh这个文件夹了。
#### 二. 数据库表的操作
1. 查看表
mysql> use zmedu;
Database changed
mysql> show tables;
+-----------------+
| Tables_in_zmedu |
+-----------------+
| t |
+-----------------+
1 row in set
mysql>
zmedu数据库里我创建了一个t表，所以使用show就可以看到，zmedu库中只有一个表t。
2. 创建表
语法：create table 表名 (字段名 类型, 字段名 类型, 字段名 类型);
mysql> create table hero(id int(20),name char(40),level int(2));
Query OK, 0 rows affected
mysql> show tables;
+-----------------+
| Tables_in_zmedu |
+-----------------+
| hero |
| t |
+-----------------+
2 rows in set
3. 查看表结构的表述
mysql> desc hero;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| name | char(40) | YES | | NULL | |
| level | int | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
3 rows in set
可以看到有三个字段，id，name 和level，他们的类型
如果想查看创建表时候所执行的命令：
mysql> show create table hero;
+-------+--------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------+
| hero | CREATE TABLE `hero` (
`id` int DEFAULT NULL,
`name` char(40) DEFAULT NULL,
`level` int DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set
mysql>
在MySQL8里，创建表的默认 编码是UTF8
4. 删除表
mysql> create table hero1(id int(20),name char(40),level int(2));
Query OK, 0 rows affected
mysql> show tables;
+-----------------+
| Tables_in_zmedu |
+-----------------+
| hero |
| hero1 |
| t |
+-----------------+
3 rows in set
mysql> drop table hero1;
Query OK, 0 rows affected
mysql> show tables;
+-----------------+
| Tables_in_zmedu |
+-----------------+
| hero |
| t |
+-----------------+
2 rows in set
5. 插入记录
使用insert into插入数据， insert into ..values
mysql> insert into hero values(1,'zmgaosh',20);
Query OK, 1 row affected
mysql> insert into hero(id,name) values(2,'gaosh
');
Query OK, 1 row affected
6. 查看表记录
mysql> select * from hero;
+----+---------+-------+
| id | name | level |
+----+---------+-------+
| 1 | zmgaosh | 20 |
| 2 | gaosh | NULL |
+----+---------+-------+
2 rows in set
只查某一个字段
mysql> select id from hero;
+----+
| id |
+----+
| 1 |
| 2 |
+----+
2 rows in set
mysql>
字段的操作
1. 修改字段类型
查看一下原来的字段结构
mysql> desc hero;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| name | char(40) | YES | | NULL | |
| level | int | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
3 rows in set
可以看到有id，name ，level 类型
我们现在把name的char类型改为varchar;
mysql> alter table hero modify name varchar(4
0);
Query OK, 2 rows affected
Records: 2 Duplicates: 0 Warnings: 0
mysql> desc hero;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| name | varchar(40) | YES | | NULL | |
| level | int | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
3 rows in set
2. 修改字段名称和类型
语法： alter table 表名 change 原字段名 新字段名 新字段类型
mysql> alter table hero change name heroname char(40);
Query OK, 2 rows affected
Records: 2 Duplicates: 0 Warnings: 0
mysql> desc hero;
+----------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| heroname | char(40) | YES | | NULL | |
| level | int | YES | | NULL | |
+----------+----------+------+-----+---------+-------+
3 rows in set
3. 添加字段
语法： alter table 表名 add 字段 类型
mysql> alter table hero add team enum('A','B
');
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc hero;
+----------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| heroname | char(40) | YES | | NULL | |
| level | int | YES | | NULL | |
| team | enum('A','B') | YES | | NULL | |
+----------+---------------+------+-----+---------+-------+
4 rows in set
mysql>
4. 删除字段
语法：alter table 表名 drop 字段名 ;
mysql> desc hero;
+----------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+---------------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| heroname | char(40) | YES | | NULL | |
| level | int | YES | | NULL | |
| team | enum('A','B') | YES | | NULL | |
+----------+---------------+------+-----+---------+-------+
4 rows in set
mysql> alter table hero drop team;
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc hero;
+----------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------+------+-----+---------+-------+
| id | int | YES | | NULL | |
| heroname | char(40) | YES | | NULL | |
| level | int | YES | | NULL | |
+----------+----------+------+-----+---------+-------+
3 rows in set
5. 删除行
删除id=2的行
mysql> select * from hero;
+----+----------+-------+
| id | heroname | level |
+----+----------+-------+
| 1 | zmgaosh | 20 |
| 2 | gaosh | NULL |
+----+----------+-------+
2 rows in set
mysql> delete from hero where id=2;
Query OK, 1 row affected
mysql> select * from hero;
+----+----------+-------+
| id | heroname | level |
+----+----------+-------+
| 1 | zmgaosh | 20 |
+----+----------+-------+
1 row in set
6. 更新
更新id1 变成22
mysql> select * from hero;
+----+----------+-------+
| id | heroname | level |
+----+----------+-------+
| 1 | zmgaosh | 20 |
+----+----------+-------+
1 row in set
mysql> update hero set id=22;
Query OK, 1 row affected
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from hero;
+----+----------+-------+
| id | heroname | level |
+----+----------+-------+
| 22 | zmgaosh | 20 |
+----+----------+-------+
1 row in set
总结
数据库和数据库表的增删改查是一个运维必会的，如果连这都不会，就放弃运维了。
