一、插入数据INSERT
语法一:
INSERT INTO 表名(字段1, 字段2, 字段3…字段n) VALUES(值1, 值2, 值3…值n);
语法二:
INSERT INTO 表名 VALUES(值1, 值2, 值3…值n);
2.指定字段插入数据
语法:
INSERT INTO 表名(字段1, 字段2, 字段3…) VALUES(值1, 值2, 值3…);
3.插入多条记录
语法:
INSERT INTO 表名 VALUES
(值1, 值2, 值3…值n),
(值1, 值2, 值3…值n),
(值1, 值2, 值3…值n);
4.插入查询结果
语法:
INSERT INTO 表名(字段1, 字段2, 字段3…字段n)
SELECT(字段1, 字段2, 字段3…字段n) FROM 表2
WHERE …;
二、更新数据UPDATE
语法:
UPDATE 表名 SET
字段1=值1,
字段2=值2,
WHERE CONDITION;
示例:
UPDATE mysql.user SET password=password(‘123’) where user=’root’ and host=’localhost’;
三、删除数据DELETE
语法:
DELETE FROM 表名
WHERE CONITION;
示例:
DELETE FROM mysql.user
WHERE password=’’;
四、权限管理
#创建用户
create user 'egon'@'1.1.1.1' identified by '123';
create user 'egon'@'192.168.1.%' identified by '123';
create user 'egon'@'%' identified by '123';
#授权:对文件夹,对文件,对文件某一字段的权限
查看帮助:help grant
常用权限有:select,update,alter,delete
all可以代表除了grant之外的所有权限
#针对所有库的授权:*.* grant select on *.* to 'li'@'localhost' identified by '123'; #只在user表中可以查到li用户的select权限被设置为Y #针对某一数据库:db1.* grant select on db1.* to 'wang'@'%' identified by '123'; #只在db表中可以查到wang用户的select权限被设置为Y #针对某一个表:db1.t1 grant select on db1.t1 to 'tom'@'%' identified by '123'; #只在tables_priv表中可以查到tom用户的select权限 #针对某一个字段: mysql> select * from t3; +------+-------+------+ | id | name | age | +------+-------+------+ | 1 | egon1 | 18 | | 2 | egon2 | 19 | | 3 | egon3 | 29 | +------+-------+------+ grant select (id,name),update (age) on db1.t3 to 'egon4'@'localhost' identified by '123'; #可以在tables_priv和columns_priv中看到相应的权限 mysql> select * from tables_priv where user='egon4'\G mysql> select * from columns_priv where user='egon4'\G #删除权限 revoke select on db1.* to 'alex'@'%';
五、mysql单表查询
1、单表查询的语法
SELECT 字段1,字段2... FROM 表名
WHERE 条件
GROUP BY field
HAVING 筛选
ORDER BY field
LIMIT 限制条数
2、关键字的执行优先级
from #找到表
where #拿着where指定的约束条件,去文件/表中取出一条条记录
group by #将取出的一条条记录进行分组group by,如果没有group by,则整体作为一组
having #将分组的结果进行having过滤
select #执行select
distinct #去重
order by #将结果按条件排序
limit #限制结果的显示条数
3、简单查询
#创建表 create database company; use company; create table employee( id int not null unique auto_increment, name varchar(20) not null, sex enum('male','female') not null default 'male', age int(3) unsigned not null default 28, hire_date date not null, post varchar(50), post_comment varchar(100), salary double(15,2), office int, depart_id int ); #插入记录三个部门:教学,销售,运营 insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values ('wang','male',18,'20170301','teacher',7300.33,401,1), ('li','male',78,'20150302','teacher',1000000.31,401,1), ('jim','male',81,'20130305','teacher',8300,401,1), ('zhao','male',73,'20140701','teacher',3500,401,1), ('liwenzhou','male',28,'20121101','teacher',2100,401,1), ('jingliyang','female',18,'20110211','teacher',9000,401,1), ('jinxin','male',18,'19000301','teacher',30000,401,1), ('成龙','male',48,'20101111','teacher',10000,401,1), ('歪歪','female',48,'20150311','sale',3000.13,402,2), ('丫丫','female',38,'20101101','sale',2000.35,402,2), ('丁丁','female',18,'20110312','sale',1000.37,402,2), ('星星','female',18,'20160513','sale',3000.29,402,2), ('格格','female',28,'20170127','sale',4000.33,402,2), ('张野','male',28,'20160311','operation',10000.13,403,3), ('程咬金','male',18,'19970312','operation',20000,403,3), ('程咬银','female',18,'20130311','operation',19000,403,3), ('程咬铜','male',18,'20150411','operation',18000,403,3), ('程咬铁','female',18,'20140512','operation',17000,403,3) ; +----+------------+--------+-----+------------+-----------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+-----------+--------------+------------+--------+-----------+ | 1 | wang | male | 18 | 2017-03-01 | teacher | NULL | 7300.33 | 401 | 1 | | 2 | li | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 3 | jim | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 4 | zhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | | 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 | | 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 | | 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 | +----+------------+--------+-----+------------+-----------+--------------+------------+--------+-----------+ # 简单查询 SELECT id, name, sex, age, hire_date, post, post_comment, salary, office, depart_id FROM employee; SELECT * FROM employee; SELECT name, salary FROM employee; # 避免重复DISTINCT SELECT DISTINCT post FROM employee; +-----------+ | post | +-----------+ | teacher | | sale | | operation | +-----------+ # 通过四则运算查询 SELECT name, salary * 12 FROM employee; SELECT name, salary * 12 AS Annual_salary FROM employee; SELECT name, salary * 12 Annual_salary FROM employee; +------------+---------------+ | name | Annual_salary | +------------+---------------+ | wang | 87603.96 | | li | 12000003.72 | | jim | 99600.00 | | zhao | 42000.00 | | liwenzhou | 25200.00 | | jingliyang | 108000.00 | | jinxin | 360000.00 | | 成龙 | 120000.00 | | 歪歪 | 36001.56 | | 丫丫 | 24004.20 | | 丁丁 | 12004.44 | | 星星 | 36003.48 | | 格格 | 48003.96 | | 张野 | 120001.56 | | 程咬金 | 240000.00 | | 程咬银 | 228000.00 | | 程咬铜 | 216000.00 | | 程咬铁 | 204000.00 | +------------+---------------+ # 定义显示格式 CONCAT() 函数用于连接字符串 SELECT CONCAT('姓名: ', name, ' 年薪: ', salary * 12) AS Annual_salary FROM employee; CONCAT_WS() 第一个参数为分隔符 SELECT CONCAT_WS(':', name, salary * 12) AS Annual_salary FROM employee; +----------------------+ | Annual_salary | +----------------------+ | wang:87603.96 | | li:12000003.72 | | jim:99600.00 | | zhao:42000.00 | | liwenzhou:25200.00 | | jingliyang:108000.00 | | jinxin:360000.00 | | 成龙:120000.00 | | 歪歪:36001.56 | | 丫丫:24004.20 | | 丁丁:12004.44 | | 星星:36003.48 | | 格格:48003.96 | | 张野:120001.56 | | 程咬金:240000.00 | | 程咬银:228000.00 | | 程咬铜:216000.00 | | 程咬铁:204000.00 | +----------------------+练习:
(1)查出所有员工的名字,薪资,格式为
<名字:egon> <薪资:3000>
(2)查出所有的岗位(去掉重复)
(3)查出所有员工名字,以及他们的年薪,年薪的字段名为annual_year
select concat('<名字:',name,'> ','<薪资:',salary,'>') from employee; select distinct depart_id from employee; select name,salary*12 annual_salary from employee;
4、WHERE约束
# 1:单条件查询 SELECT name FROM employee WHERE post = 'sale'; # 2:多条件查询 SELECT name, salary FROM employee WHERE post = 'teacher' AND salary > 10000; # 3:关键字BETWEEN AND SELECT name, salary FROM employee WHERE salary BETWEEN 10000 AND 20000; SELECT name, salary FROM employee WHERE salary NOT BETWEEN 10000 AND 20000; # 4:关键字IS NULL(判断某个字段是否为NULL不能用等号,需要用IS) SELECT name, post_comment FROM employee WHERE post_comment IS NULL; SELECT name, post_comment FROM employee WHERE post_comment IS NOT NULL; SELECT name, post_comment FROM employee WHERE post_comment = ''; #注意''是空字符串,不是null ps: 执行 update employee set post_comment = '' where id = 2; 再用上条查看,就会有结果了 # 5:关键字IN集合查询 SELECT name, salary FROM employee WHERE salary = 3000 OR salary = 3500 OR salary = 4000 OR salary = 9000; SELECT name, salary FROM employee WHERE salary IN(3000, 3500, 4000, 9000); SELECT name, salary FROM employee WHERE salary NOT IN(3000, 3500, 4000, 9000); # 6:关键字LIKE模糊查询 通配符’ % ’ SELECT * FROM employee WHERE name LIKE 'eg%'; 通配符’_’ SELECT * FROM employee WHERE name LIKE 'al__';
练习:
(1)查看岗位是teacher的员工姓名、年龄
(2)查看岗位是teacher且年龄大于30岁的员工姓名、年龄
(3)查看岗位是teacher且薪资在9000-1000范围内的员工姓名、年龄、薪资
(4)查看岗位描述不为NULL的员工信息
(5)查看岗位是teacher且薪资是10000或9000或30000的员工姓名、年龄、薪资
(6)查看岗位是teacher且薪资不是10000或9000或30000的员工姓名、年龄、薪资
(7)查看岗位是teacher且名字是jin开头的员工姓名、年薪
select name,age from employee where post = 'teacher'; select name,age from employee where post='teacher' and age > 30; select name,age,salary from employee where post='teacher' and salary between 9000 and 10000; select * from employee where post_comment is not null; select name,age,salary from employee where post='teacher' and salary in (10000,9000,30000); select name,age,salary from employee where post='teacher' and salary not in (10000,9000,30000); select name,salary*12 from employee where post='teacher' and name like 'jin%'; mysql> select name,salary*12 as year_salary from employee where post='teacher' and name like 'jin%';
5、分组查询:GROUP BY
(1)GROUP BY
单独使用GROUP BY关键字分组
SELECT post FROM employee GROUP BY post;
注意:我们按照post字段分组,那么select查询的字段只能是post,想要获取组内的其他相关信息,需要借助函数
GROUP BY关键字和GROUP_CONCAT()函数一起使用
SELECT post,GROUP_CONCAT(name) FROM employee GROUP BY post; #按照岗位分组,并查看组内成员名
SELECT post,GROUP_CONCAT(name) as emp_members FROM employee GROUP BY post;
GROUP BY与聚合函数一起使用
select post,count(id) as count from employee group by post; #按照岗位分组,并查看每个组有多少人
如果我们用unique的字段作为分组的依据,则每一条记录自成一组,这种分组没有意义
多条记录之间的某个字段值相同,该字段通常用来作为分组的依据
(2)聚合函数
#强调:聚合函数聚合的是组的内容,若是没有分组,则默认一组
示例:
SELECT COUNT(*) FROM employee;
SELECT COUNT(*) FROM employee WHERE depart_id=1;
SELECT MAX(salary) FROM employee;
SELECT MIN(salary) FROM employee;
SELECT AVG(salary) FROM employee;
SELECT SUM(salary) FROM employee;
SELECT SUM(salary) FROM employee WHERE depart_id=3;
练习:
(1)查询岗位名以及岗位包含的所有员工名字
(2)查询岗位名以及各岗位内包含的员工个数
(3)查询公司内男员工和女员工的个数
(4)查询岗位名以及各岗位的平均薪资
(5)查询岗位名以及各岗位的最高薪资
(6)查询岗位名以及各岗位的最低薪资
(7)查询男员工与男员工的平均薪资,女员工与女员工的平均薪资
mysql> select post,group_concat(name) from employee group by post; mysql> select post,count(id) from employee group by post; mysql> select sex,count(id) from employee group by sex; mysql> select post,avg(salary) from employee group by post; mysql> select post,max(salary) from employee group by post; mysql> select post,min(salary) from employee group by post; mysql> select sex,avg(salary) from employee group by sex;
6、HAVING过滤
HAVING与WHERE不一样的地方在于!!!!!!
#!!!执行优先级从高到低:where > group by > having
#1. Where 发生在分组group by之前,因而Where中可以有任意字段,但是绝对不能使用聚合函数。
#2. Having发生在分组group by之后,因而Having中可以使用分组的字段,无法直接取到其他字段,可以使用聚合函数
练习:
1. 查询各岗位内包含的员工个数小于2的岗位名、岗位内包含员工名字、个数
2. 查询各岗位平均薪资大于10000的岗位名、平均工资
3. 查询各岗位平均薪资大于10000且小于20000的岗位名、平均工资
mysql> select post,group_concat(name),count(id) from employee group by post having count(id) < 2; mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000; mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 and avg(salary) <20000;
7、查询排序:ORDER BY
按单列排序
SELECT * FROM employee ORDER BY salary;
SELECT * FROM employee ORDER BY salary ASC;
SELECT * FROM employee ORDER BY salary DESC;
按多列排序:先按照age排序,如果年纪相同,则按照薪资排序
SELECT * from employee ORDER BY age,salary DESC;
练习:
1. 查询所有员工信息,先按照age升序排序,如果age相同则按照hire_date降序排序
2. 查询各岗位平均薪资大于10000的岗位名、平均工资,结果按平均薪资升序排列
3. 查询各岗位平均薪资大于10000的岗位名、平均工资,结果按平均薪资降序排列
mysql> select * from employee ORDER BY age asc,hire_date desc; mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 order by avg(salary) asc; mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 order by avg(salary) desc;
8、限制查询的记录数:LIMIT
SELECT * FROM employee ORDER BY salary DESC LIMIT 3; # 默认初始位置为0 SELECT * FROM employee ORDER BY salary DESC LIMIT 0, 5; # 从第0开始,即先查询出第一条,然后包含这一条在内往后查5条 SELECT * FROM employee ORDER BY salary DESC LIMIT 5, 5; # 从第5开始,即先查询出第6条,然后包含这一条在内往后查5条
练习:分页显示,每页5条
mysql> select * from employee limit 0,5; #显示第1到5条记录 mysql> select * from employee limit 5,5; #显示第5到10条记录 mysql> select * from employee limit 10,5; #显示第10到15条记录
9、使用正则表达式查询
SELECT * FROM employee WHERE name REGEXP '^ale'; SELECT * FROM employee WHERE name REGEXP 'on$'; SELECT * FROM employee WHERE name REGEXP 'm{2}';
小结:对字符串匹配的方式
WHERE name = 'li';
WHERE name LIKE 'yua%';
WHERE name REGEXP 'on$';
练习:
查看所有员工中名字是jin开头,n或者g结果的员工信息
select * from employee where name regexp '^jin.*[gn]$';
六、mysql多表查询
1、建表
create table department(id int,name varchar(20)); create table employee( id int primary key auto_increment, name varchar(20), sex enum('male','female') not null default 'male', age int, dep_id int ); #插入数据 insert into department values(200,'技术'),(201,'人力资源'),(202,'销售'),(203,'运营'); insert into employee(name,sex,age,dep_id) values ('egon','male',18,200), ('alex','female',48,201), ('wupeiqi','male',38,201), ('yuanhao','female',28,202), ('liwenzhou','male',18,200), ('jingliyang','female',18,204) ;
2、多表连接查询
(1)交叉连接:不适用任何匹配条件。生成笛卡尔积
mysql> select * from department; +------+--------------+ | id | name | +------+--------------+ | 200 | 技术 | | 201 | 人力资源 | | 202 | 销售 | | 203 | 运营 | +------+--------------+ mysql> select * from employee; +----+------------+--------+------+--------+ | id | name | sex | age | dep_id | +----+------------+--------+------+--------+ | 1 | egon | male | 18 | 200 | | 2 | alex | female | 48 | 201 | | 3 | wupeiqi | male | 38 | 201 | | 4 | yuanhao | female | 28 | 202 | | 5 | liwenzhou | male | 18 | 200 | | 6 | jingliyang | female | 18 | 204 | +----+------------+--------+------+--------+ mysql> select * from employee,department;
(2)内连接:只连接匹配的行
#找两张表共有的部分,相当于利用条件从笛卡尔积结果中筛选出了正确的结果
#department没有204这个部门,因而employee表中关于204这条员工信息没有匹配出来
mysql> select employee.id,employee.name,employee.age,employee.sex,department.name from employee inner join department on employee.dep_id=department.id; +----+-----------+------+--------+--------------+ | id | name | age | sex | name | +----+-----------+------+--------+--------------+ | 1 | egon | 18 | male | 技术 | | 2 | alex | 48 | female | 人力资源 | | 3 | wupeiqi | 38 | male | 人力资源 | | 4 | yuanhao | 28 | female | 销售 | | 5 | liwenzhou | 18 | male | 技术 | +----+-----------+------+--------+--------------+ mysql> select employee.id,employee.name,employee.age,employee.sex,department.name from employee,department where employee.dep_id=department.id;
(3)外链接之左连接:优先显示左表全部记录
#以左表为准,即找出所有员工信息,当然包括没有部门的员工
#本质就是:在内连接的基础上增加左边有右边没有的结果
mysql> select employee.id,employee.name,department.name as depart_name from employee left join department on employee.dep_id=department.id; +----+------------+--------------+ | id | name | depart_name | +----+------------+--------------+ | 1 | egon | 技术 | | 5 | liwenzhou | 技术 | | 2 | alex | 人力资源 | | 3 | wupeiqi | 人力资源 | | 4 | yuanhao | 销售 | | 6 | jingliyang | NULL | +----+------------+--------------+
(4)外链接之右连接:优先显示右表全部记录
#以右表为准,即找出所有部门信息,包括没有员工的部门
#本质就是:在内连接的基础上增加右边有左边没有的结果
mysql> select employee.id,employee.name,department.name as depart_name from employee right join department on employee.dep_id=department.id; +------+-----------+--------------+ | id | name | depart_name | +------+-----------+--------------+ | 1 | egon | 技术 | | 2 | alex | 人力资源 | | 3 | wupeiqi | 人力资源 | | 4 | yuanhao | 销售 | | 5 | liwenzhou | 技术 | | NULL | NULL | 运营 | +------+-----------+--------------+
(5)全外连接:显示左右两个表全部记录
全外连接:在内连接的基础上增加左边有右边没有的和右边有左边没有的结果
#注意:mysql不支持全外连接 full JOIN
#强调:mysql可以使用此种方式间接实现全外连接
select * from employee left join department on employee.dep_id = department.id union select * from employee right join department on employee.dep_id = department.id ; +------+------------+--------+------+--------+------+--------------+ | id | name | sex | age | dep_id | id | name | +------+------------+--------+------+--------+------+--------------+ | 1 | egon | male | 18 | 200 | 200 | 技术 | | 5 | liwenzhou | male | 18 | 200 | 200 | 技术 | | 2 | alex | female | 48 | 201 | 201 | 人力资源 | | 3 | wupeiqi | male | 38 | 201 | 201 | 人力资源 | | 4 | yuanhao | female | 28 | 202 | 202 | 销售 | | 6 | jingliyang | female | 18 | 204 | NULL | NULL | | NULL | NULL | NULL | NULL | NULL | 203 | 运营 | +------+------------+--------+------+--------+------+--------------+ #注意 union与union all的区别:union会去掉相同的纪录
3、符合条件连接查询
#示例1:以内连接的方式查询employee和department表,并且employee表中的age字段值必须大于25,即找出年龄大于25岁的员工以及员工所在的部门 select employee.name,department.name from employee inner join department on employee.dep_id = department.id where age > 25; +---------+--------------+ | name | name | +---------+--------------+ | alex | 人力资源 | | wupeiqi | 人力资源 | | yuanhao | 销售 | +---------+--------------+ #示例2:以内连接的方式查询employee和department表,并且以age字段的升序方式显示 select employee.id,employee.name,employee.age,department.name from employee,department where employee.dep_id = department.id and age > 25 order by age asc; +----+---------+------+--------------+ | id | name | age | name | +----+---------+------+--------------+ | 4 | yuanhao | 28 | 销售 | | 3 | wupeiqi | 38 | 人力资源 | | 2 | alex | 48 | 人力资源 | +----+---------+------+--------------+
4、子查询
#1:子查询是将一个查询语句嵌套在另一个查询语句中。
#2:内层查询语句的查询结果,可以为外层查询语句提供查询条件。
#3:子查询中可以包含:IN、NOT IN、ANY、ALL、EXISTS 和 NOT EXISTS等关键字
#4:还可以包含比较运算符:= 、 !=、> 、<等
(1)带IN关键字的子查询
#查询平均年龄在25岁以上的部门名 select id,name from department where id in (select dep_id from employee group by dep_id having avg(age) > 25); #查看技术部员工姓名 select name from employee where dep_id in (select id from department where name='技术'); #查看不足1人的部门名(子查询得到的是有人的部门id) select name from department where id not in (select distinct dep_id from employee);
(2)带比较运算符的子查询
#比较运算符:=、!=、>、>=、<、<=、<>
#查询大于所有人平均年龄的员工名与年龄 mysql> select name,age from emp where age > (select avg(age) from emp); #查询大于部门内平均年龄的员工名、年龄 select t1.name,t1.age from emp t1 inner join (select dep_id,avg(age) avg_age from emp group by dep_id) t2 on t1.dep_id = t2.dep_id where t1.age > t2.avg_age;
(3)带EXISTS关键字的子查询
EXISTS关字键字表示存在。在使用EXISTS关键字时,内层查询语句不返回查询的记录。
而是返回一个真假值。True或False
当返回True时,外层查询语句将进行查询;当返回值为False时,外层查询语句不进行查询
#department表中存在dept_id=203,Ture mysql> select * from employee where exists (select id from department where id=200); #department表中存在dept_id=205,False mysql> select * from employee where exists (select id from department where id=204);