mysql数据查询及用户授权

SQL语句 

DDL		数据定义语言
	create, drop, alter
DML		数据操纵语言
	insert, delete, update, select 
DCL		数据控制语言
	grant, revoke

SQL语句

DDL		数据定义语言
	create, drop, alter
DML		数据操纵语言
	insert, delete, update, select 
DCL		数据控制语言
	grant, revoke

以下例子以 jiaowu.sql 里面的数据为例子：
如需可以找我索要
数据查询

单表查询
多表查询/连接查询 
嵌套查询/子查询

一、单表查询

select 字段名称, 字段名称, .... from 表名 [查询条件]

	mysql> select Tname, Age from tutors;
	
	mysql> select * from tutors;

	mysql> select Tname as 教师姓名, Age as 年龄 from tutors;
	
	mysql> select Tname 教师姓名, Age  年龄 from tutors;

查询条件

1、where 条件

条件写法：
	=, !=, >, >=, <=, <
	and, or, not

mysql> select Tname from tutors where Age > 80;

mysql> select * from tutors where Tname='YiDeng';


and 并且 

	between n and m 

		mysql> select Tname from tutors where Age >= 70 and Age <= 80;

		mysql> select Tname from tutors where Age between 70 and 80;
	

or  或者 
	
	in(v1, v2, v3)

	mysql> select * from tutors where Tname="YiDeng" or Tname = "HuYidao" or Tname = "YuCanghai";

	mysql> select * from tutors where Tname in ("YiDeng", "HuYiDao", "YuCanghai");


not   取反 

	mysql> select * from tutors where not Age > 80;


模糊查询

	1) like 通配符表达式 
	
		通配符： 
			%	任意字符 
			_	任意单个字符 

		mysql> select Tname from tutors where Tname like "%eng%";


	2) rlike 正则表达式 
	
		mysql> select Tname from tutors where Tname rlike "ing";

		mysql> select Tname from tutors where Tname rlike "^[HJY]";



is null
is not null 

	mysql> select Name from students where CID2 is null;

	mysql> select Name from students where CID2 is not null;

2、排序

order by 字段名称 [ASC|DESC]

	DESC: 降序

	mysql> select Tname, Age from tutors order by Age;

	mysql> select Tname, Age from tutors order by Age DESC;

	mysql> select Tname, Age from tutors where Age > 70 order by Age;

3、限制查询结果的数量

limit n[,m]

	mysql> select * from tutors limit 4, 1;

	mysql> select Tname, Age from tutors where Tname rlike "^[HYJ]" order by Age DESC limit 1;

4、使用聚合函数 / 分组

聚合函数：
	sum()
	max()
	min()
	avg()
	count() 
	
mysql> select avg(Age) as 平均年龄 from tutors;

mysql> select count(*) from tutors where Age > 80;


分组：
	group by 字段名称 HAVING 条件 
	
		mysql> select avg(Age) as 平均年龄, gender as 性别 from tutors group by Gender ;
	
		mysql> select count(*) as 人数, gender as 性别 from tutors group by Gender ;

		mysql> select avg(Age) as 平均年龄, gender as 性别 from tutors group by Gender having 平均年龄>65;

5、去重

distinct 

	mysql> select distinct name from tb01;

	mysql> select distinct name, password from tb01;

二、多表查询/连接查询

前提条件：
	表之间要存在相关联的字段 


类型：
	内连接
	外连接
		左外连接
		右外连接

内连接

只有相关联字段具有相同的值时，才会显示结果

语法：
	select 字段名称, 字段名称  from 表名 inner join 表名 on 相关联的字段 

	方法1) 
		
		mysql> select students.Name, students.Age, students.Gender, tutors.Tname from students inner join tutors on students.TID=tutors.TID;
	
		mysql> select students.Name, courses.Cname from students inner join courses on students.CID1=courses.CID;

		mysql> select students.Name, courses.Cname, tutors.Tname from students inner join courses inner join tutors on students.CID1=courses.CID and courses.TID=tutors.TID;


	方法2) 
	
		mysql> select students.Name , students.Age , students.Gender , tutors.Tname from students, tutors where students.TID=tutors.TID;

外连接
左外连接
右外连接

左外连接

	以左表为主，显示左表所有数据；有相关联数据时，显示，无相关联数据时，显示为NULL 
	
	语法：
		select 字段名称, 字段名称  from 表名 left join 表名 on 相关联的字段 

	mysql> select students.Name, students.Age , students.Gender, courses.Cname from students left join courses on students.CID1=courses.CID;


右外连接

	以右表为主，显示右表所有数据；有相关联数据时，显示，无相关联数据时，显示为NULL 
	
	语法：
		select 字段名称, 字段名称  from 表名 right join 表名 on 相关联的字段 

	mysql> select students.Name, students.Age , students.Gender, courses.Cname from courses right join students on students.CID1=courses.CID;


视图 view
	
	临时表 

	作用：用于保存多表查询的结果，避免多表查询产生交叉连接
	
1、创建视图

	语法：
		create view view_name as select_state 
		
	mysql> create view student_tutor_name
		-> as
		-> select students.Name, students.Age, students.Gender, tutors.Tname from students inner join tutors on students.TID=tutors.TID;


2、删除视图

	mysql> drop view student_tutor_name;

三、嵌套查询

将一个查询的结果作为另一个查询的条件

mysql> select Tname, Gender , Age from tutors where Age > (select avg(Age) from tutors);

mysql> select Name from students where Age in (select Age from tutors);

用户、权限

用户管理

1、用户名格式

	username@host
		
		host写法：
			1、允许本机登录   localhost 
			2、IP地址         [email protected] 
			3、网段 		  [email protected].%   
			4、主机名         martin@controller 
			5、所有			  martin@% 

2、用户存储位置  

	mysql.user表 
	
	# select user, host from mysql.user; 

1、删除用户

drop user 'martin'@'1.1.1.1';

2、创建用户

create user user@host identified by 'password' 


示例1： 

	mysql> create user 'martin'@'localhost' identified by 'WWW.1.com';
	mysql> flush privileges;
	
	mysql> select current_user();			//查看当前登录的用户 
	+------------------+
	| current_user()   |
	+------------------+
	| martin@localhost |
	+------------------+
	1 row in set (0.00 sec)


示例2：

	mysql> create user 'martin'@'192.168.122.69' identified by 'WWW.1.com';

	mysql> flush privileges;


	登录远程数据库服务器
	
	[root@client_01 ~]# mysql -u martin -p -h 192.168.122.250

3、更改用户密码

1) set password for ...

	mysql> set password for 'martin'@'192.168.122.69' = PASSWORD("WWW.2.com");

	mysql> flush privileges;


2) 更新user表 

	mysql> update mysql.user set authentication_string=PASSWORD("WWW.3.com") where user="martin" and host="192.168.122.69";
	mysql> flush privileges;

4、重置root密码

1) 编辑my.cnf配置文件 

	[mysqld]
		skip-grant-tables=1
	
2) 重启mysql服务 

3) 登录数据，使用Update修改密码 

4) 删除配置文件skip-grant-tables选项，重启服务 

权限

1、授权

grant 权限1, 权限2 on 库名.表名 to 用户名 [identified by "password"]

	权限： 
		create, drop, select, update, delete, insert, alter 
		all 

	库名.表名
		jiaowu.tutors 
		jiowu.* 
		*.* 

	
		mysql> grant select on jiaowu.tutors to 'martin'@'192.168.122.69';
		mysql> flush privileges;


		mysql> grant all on jiaowu.* to 'martin'@'192.168.122.69';
		mysql> flush privileges;

	
		针对update，mysql支持对每个字段授权 
		

		mysql> grant select, update(Age) on jiaowu.students to 'martin'@'192.168.122.69';
		mysql> flush privileges;

	
		授权、同时创建用户
		
		mysql> grant all on jiaowu.* to 'robin'@'192.168.122.69' identified by 'WWW.1.com';

		mysql> flush privileges;

2、查看权限

mysql> show grants for 'martin'@'192.168.122.69';

3、撤销权限

mysql> revoke select on jiaowu.tutors from 'martin'@'192.168.122.69';
mysql> flush privileges;

=================================================================================
事务

1、启动事务

mysql>  start transaction;

2、提交事务

mysql> commit ; 

3、回滚

mysql> rollback;

=================================================================================

在shell终端执行SQL

[root@mysql_server ~]# mysql -uroot -pWWW.1.com -e "select * from jiaowu.tb01"

[root@mysql_server ~]# mysql -uroot -pWWW.1.com -e "show databases"

[root@mysql_server ~]# mysql -uroot -pWWW.1.com -e "select * from jiaowu.tb01" 2> /dev/null