Mysql数据库操作

一、SQL 语句概述

SQL 语言是(Structured Query Language 的缩写，即结构化查询语言)，是关系型数据库 的标准语言，用于维护管理数据库，如数据查询、数据更新、访问控制、对象管理等功能。

SQL 分类:

• DDL:数据定义语言，用于增删改数据库的对象，如库、表、索引等
• DML:数据操纵语言，用于对表中的数据进行增删改
• DQL:数据查询语言，用于数据查询
• DCL:数据控制语言

二、MySQL 数据库表的管理操作

注:大部分命令不区分大小写

1、查看数据库结构

查看数据库列表信息

格式:show databases;

示例:

[root@mysql-master ~]# netstat -utpln |grep mysql

tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      13123/mysqld

[root@mysql-master ~]# mysql -u root -p

Enter password:123123

mysql>show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.01 sec)

查看数据库中的数据表信息

格式:

use 数据库名;

show tables;

示例：

mysql> use mysql;

Database changed

mysql> show tables;
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
| columns_priv              |
| db                        |
| event                     |
| func                      |
| general_log               |
| help_category             |
......

显示数据表的结构(字段)

格式:

describe [数据库.]表名;

示例：

mysql> describe mysql.user;
+------------------------+-----------------------------------+------+-----+---------+-------+
| Field                  | Type                              | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+---------+-------+
| Host                   | char(60)                          | NO   | PRI |         |       |
| User                   | char(16)                          | NO   | PRI |         |       |
.....

mysql> use mysql;

Database changed

mysql> describe user;

+------------------------+-----------------------------------+------+-----+---------+-------+
| Field                  | Type                              | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+---------+-------+
| Host                   | char(60)                          | NO   | PRI |         |       |
| User                   | char(16)                          | NO   | PRI |         |       |

2、DDL 语句操作

数据定义语言，用于增删改数据库的对象，如库、表、索引等

create 创建新库、创建新表

格式:

create database 数据库名;

create table 表名 (定义字段);

示例：

mysql> create database auth;     //新建一个名为auth的数据库
Query OK, 1 row affected (0.01 sec)

mysql> use auth;         //使用auth这个数据库

Database changed

mysql> create table users (user_name char(20) not null,user_passwd char(30) default '',primary key(user_name));      //在auth库中，创建名为users的表，表内俩个字段为（user_name 最多20个字节 不能为空，user_passwd 最多为30个字节 默认为空，索引关键字 user_name）

Query OK, 0 rows affected (0.05 sec)

drop 删除库、删除表

格式:

drop table [数据库名.]表名;

drop database 数据库名;

注意：删除时先删表，再删库

示例:

mysql> drop table auth.users;      //删除auth库中的users表
Query OK, 0 rows affected (0.00 sec)

mysql> drop database auth;       //删除auth数据库
Query OK, 0 rows affected (0.00 sec)

3、DML 语句操作

数据操纵语言，用于对表中的数据进行增删改

insert 插入新数据

格式:

insert into 表名(字段 1,字段 2,……) values(‘字段 1 的值’,’字段 2 的值’……);

示例:

mysql> use auth;

Database changed

mysql> desc users;

+-------------+----------+------+-----+---------+-------+
| Field       | Type     | Null | Key | Default | Extra |
+-------------+----------+------+-----+---------+-------+
| user_name   | char(20) | NO   | PRI | NULL    |       |
| user_passwd | char(30) | YES  |     |         |       |
+-------------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql> insert into users(user_name,user_passwd) values ('zhangsan',password('123123'));    //在users表的（字段user_name，字段user_passwd）中添加（'zhangsan'，调用函数password（‘123123’));

Query OK, 1 row affected, 1 warning (0.01 sec)

mysql> insert into users values ('lisi',password('123456')); //字段内容可省略

Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> select * from users;

+-----------+--------------------------------+
| user_name | user_passwd                    |
+-----------+--------------------------------+
| lisi      | *6BB4837EB74329105EE4568DDA7DC |
| zhangsan  | *E56A114692FE0DE073F9A1DD68A00 |
+-----------+--------------------------------+
2 rows in set (0.00 sec)

update 更改原有数据

格式:

update 表名 set 字段名 1=值 1 [,字段 2=值 2] where 条件表达式;

示例:

mysql> update auth.users set user_passwd=password('') where user_name='lisi';      //清空lisi的密码

Query OK, 0 rows affected (0.52 sec)

Rows matched: 1  Changed: 0  Warnings: 0

mysql> select * from users;

+-----------+--------------------------------+
| user_name | user_passwd                    |
+-----------+--------------------------------+
| lisi      |                                |
| zhangsan  | *E56A114692FE0DE073F9A1DD68A00 |
+-----------+--------------------------------+

2 rows in set (0.00 sec)

mysql> update mysql.user set password=password('123123') where user='root';        //修改mysql登录root用户密码为123123

Query OK, 0 rows affected (0.00 sec)
Rows matched: 4  Changed: 0  Warnings: 0

mysql> flush privileges;   //刷新权限

Query OK, 0 rows affected (0.00 sec)

delete 删除不需要的数据

格式:

delete from 表名 where 条件表达式;

示例:

mysql> delete from auth.users where user_name='lisi';      //在auth库中的users表中，删除用户名为lisi的记录

Query OK, 1 row affected (0.01 sec)

mysql> select * from users;

+-----------+--------------------------------+
| user_name | user_passwd                    |
+-----------+--------------------------------+
| zhangsan  | *E56A114692FE0DE073F9A1DD68A00 |
+-----------+--------------------------------+
1 row in set (0.00 sec)

mysql> delete from mysql.user where user='';     //在mysql库中的user表中，删除空的用户名的记录

Query OK, 2 rows affected (0.00 sec)

4、DQL 语句操作

数据查询语言，用于数据查询

select 查询语句

​格式: select 字段名 1,字段名 2,……from 表名;

select 字段名 1,字段名 2,……from 表名 where 条件表达式;

示例:

mysql> select * from auth.users;

+-----------+--------------------------------+
| user_name | user_passwd                    |
+-----------+--------------------------------+
| zhangsan  | *E56A114692FE0DE073F9A1DD68A00 |
+-----------+--------------------------------+
1 row in set (0.00 sec)

mysql> select user_name from auth.users;

+-----------+
| user_name |
+-----------+
| zhangsan  |
+-----------+
1 row in set (0.00 sec)

mysql> select * from auth.users where user_name='zhangsan';

+-----------+--------------------------------+
| user_name | user_passwd                    |
+-----------+--------------------------------+
| zhangsan  | *E56A114692FE0DE073F9A1DD68A00 |
+-----------+--------------------------------+
1 row in set (0.00 sec)

三、案例:建立公司 IT 运营部工资数据表

​需求描述:为公司建立员工工资数据库 imployee_salary，在 imployee_salary 数据库中，建立IT_salary数据表，以保存 IT 运营部员工的工资信息，如下表所示:

建立数据库imployee_salary

mysql> show databases;

+--------------------+
| Database           |
+--------------------+
| information_schema |
| auth               |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

mysql> create database imployee_salary;

Query OK, 1 row affected (0.00 sec)

mysql> use imployee_salary;

Database changed

建立数据表

mysql> create table IT_salary (岗位类别 char(20) not null,姓名 char(20) not null,年龄 int,员工ID int not null,学历 char(6),年限 int,薪资 int not null, primary key (员工ID));  

#int 数字类型、char 字符串类型、not null 不能为空、char（）指定最多字节个数、primary key（）指定索引字段

Query OK, 0 rows affected (0.13 sec)

mysql> desc IT_salary;

+--------------+----------+------+-----+---------+-------+
| Field        | Type     | Null | Key | Default | Extra |
+--------------+----------+------+-----+---------+-------+
| 岗位类别     | char(20) | NO   |     | NULL    |       |
| 姓名         | char(20) | NO   |     | NULL    |       |
| 年龄         | int(11)  | YES  |     | NULL    |       |
| 员工ID       | int(11)  | NO   | PRI | NULL    |       |
| 学历         | char(6)  | YES  |     | NULL    |       |
| 年限         | int(11)  | YES  |     | NULL    |       |
| 薪资         | int(11)  | NO   |     | NULL    |       |
+--------------+----------+------+-----+---------+-------+
7 rows in set (0.00 sec)

将 IT 运营部的员工工资信息插入到

mysql> insert into IT_salary (岗位类别,姓名,年龄,员工ID,学历,年限,薪资) values ('网络工程师','孙空武',27,011,'本科',3,4800);

Query OK, 1 row affected (0.01 sec)

mysql> insert into IT_salary(岗位类别,姓名,年龄,员工ID,学历,年限,薪资) values('Windows 工程师','蓝 凌 ',19,012,'中专',2,3500);

Query OK, 1 row affected (0.00 sec)

mysql> insert into IT_salary(岗位类别,姓名,年龄,员工ID,学历,年限,薪资) values('Linux 工程师','姜纹 ',32,013,'本科',8,15000);

Query OK, 1 row affected (0.00 sec)

mysql> insert into IT_salary(岗位类别,姓名,年龄,员工ID,学历,年限,薪资) values('Java 软件工程师','关园', 38,014,'大专',10,16000);

Query OK, 1 row affected (0.00 sec)

mysql> insert into IT_salary(岗位类别,姓名,年龄,员工ID,学历,年限,薪资) values('硬件驱动工程师','罗 中  昆',29,015,'大专',9,16500);

Query OK, 1 row affected (0.01 sec)
注意：创建表时，字段不加 ‘’ 号，插入数据 values值时，字符串加 ‘’ ,数字不加 ‘’号

查看核对信息

mysql> select * from IT_salary;                                                                       

+-----------------------+------------+--------+----------+--------+--------+--------+
| 岗位类别              | 姓名       | 年龄   | 员工ID   | 学历   | 年限   | 薪资   |
+-----------------------+------------+--------+----------+--------+--------+--------+
| 网络工程师            | 孙空武     |     27 |       11 | 本科   |      3 |   4800 |
| Windows 工程师        | 蓝 凌      |     19 |       12 | 中专   |      2 |   3500 |
| Linux 工程师          | 姜纹       |     32 |       13 | 本科   |      8 |  15000 |
| Java 软件工程师       | 关 园      |     38 |       14 | 大专   |     10 |  16000 |
| 硬件驱动工程师        | 罗 中昆    |     29 |       15 | 大专   |      9 |  16500 |
+-----------------------+------------+--------+----------+--------+--------+--------+

5 rows in set (0.00 sec)

四、用户权限设置

1、设置用户权限(用户不存在时，则新建用户)

mysql> grant all on *.* to 'root'@'192.168.1.%' identified by '123456';
             
all: 所有权限
*.*:所有库所有表

Query OK, 0 rows affected (0.00 sec)

mysql> grant select on imployee_salary.* to 'linuxyao'@'localhost' identified by '123456';

Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;

Query OK, 0 rows affected (0.00 sec)

[root@mysql-master ~]# mysql -ulinuxyao -p123456

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.5.20-log Source distribution

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> delete from imployee_salary.IT_salary where 姓名='关园';

ERROR 1142 (42000): DELETE command denied to user 'linuxyao'@'localhost' for table 'IT_salary'

mysql> select * from imployee_salary.IT_salary;

+-----------------------+------------+--------+----------+--------+--------+--------+
| 岗位类别              | 姓名       | 年龄   | 员工ID   | 学历   | 年限   | 薪资   |
+-----------------------+------------+--------+----------+--------+--------+--------+
| 网络工程师            | 孙空武     |     27 |       11 | 本科   |      3 |   4800 |
| Windows 工程师        | 蓝 凌      |     19 |       12 | 中专   |      2 |   3500 |
| Linux 工程师          | 姜纹       |     32 |       13 | 本科   |      8 |  15000 |
| Java 软件工程师       | 关 园      |     38 |       14 | 大专   |     10 |  16000 |
| 硬件驱动工程师        | 罗 中昆    |     29 |       15 | 大专   |      9 |  16500 |
+-----------------------+------------+--------+----------+--------+--------+--------+
5 rows in set (0.00 sec)

​

2、查看用户权限

mysql> show grants;

mysql> show grants for 'linuxyao'@'localhost';

mysql> show grants for 'linuxyao'@'192.168.0.85';

3、撤销用户权限

mysql> revoke select on imployee_salary.* from 'linuxyao'@'localhost';

Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;

远程登录

mysql> grant all on *.* to 'linuxyao'@'%' identified by '123123';

Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;

Query OK, 0 rows affected (0.00 sec)

若宿主机连接报错，查看权限设置是否正确，可尝试如下命令:

mysql> GRANT ALL PRIVILEGES ON *.* TO 'amber'@'%' IDENTIFIED BY '123123' WITH GRANT OPTION;

mysql> FLUSH PRIVILEGES;