1. 插入完整数据（顺序插入）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2WHERE …;

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’;

语法：DELETE FROM 表名 WHERE CONITION;示例：DELETE FROM mysql.user WHERE password=’’;请空表：truncate 表;

SELECT 字段1,字段2... FROM 表名WHERE 条件GROUP BY fieldHAVING 筛选ORDER BY fieldLIMIT 限制条数注：以上语法顺序不可以置换！！！

#创建表
create table employee(
id int not null unique auto_increment,
name varchar(20) not null,
sex enum('male','female') not null default 'male', #大部分是男的
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, #一个部门一个屋子
depart_id int
);#查看表结构
mysql> desc employee;
+--------------+-----------------------+------+-----+---------+----------------+
| Field        | Type                  | Null | Key | Default | Extra          |
+--------------+-----------------------+------+-----+---------+----------------+
| id           | int(11)               | NO   | PRI | NULL    | auto_increment |
| name         | varchar(20)           | NO   |     | NULL    |                |
| sex          | enum('male','female') | NO   |     | male    |                |
| age          | int(3) unsigned       | NO   |     | 28      |                |
| hire_date    | date                  | NO   |     | NULL    |                |
| post         | varchar(50)           | YES  |     | NULL    |                |
| post_comment | varchar(100)          | YES  |     | NULL    |                |
| salary       | double(15,2)          | YES  |     | NULL    |                |
| office       | int(11)               | YES  |     | NULL    |                |
| depart_id    | int(11)               | YES  |     | NULL    |                |
+--------------+-----------------------+------+-----+---------+----------------+#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
('egon','male',18,'20170301','老男孩驻沙河办事处外交大使',7300.33,401,1), #以下是教学部
('alex','male',78,'20150302','teacher',1000000.31,401,1),
('wupeiqi','male',81,'20130305','teacher',8300,401,1),
('yuanhao','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),#以下是销售部门
('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), #以下是运营部门
('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)
;#ps：如果在windows系统中，插入中文字符，select的结果为空白，可以将所有字符编码统一设置成gbk

#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;    #通过四则运算查询SELECT name, salary*12 FROM employee;　　 以下两条命令作用一样：SELECT name, salary*12 AS Annual_salary FROM employee;SELECT name, salary*12 Annual_salary FROM employee;#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;

where字句中可以使用：1. 比较运算符：> < >= <= <> !=2. between 80 and 100 值在80到100之间，包括80和1003. in(80,90,100) 值是80或90或1004. like 'egon%'pattern可以是%或_，%表示任意多字符_表示任意一个字符 5. 逻辑运算符：在多个条件直接可以使用逻辑运算符 and or not

#1:单条件查询
    SELECT name FROM employeeWHERE post='sale';#2:多条件查询
    SELECT name,salary FROM employeeWHERE 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nullps：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
select name,age from employee where post='teacher';2. 查看岗位是teacher且年龄大于30岁的员工姓名、年龄
select name,age from employee where post='teacher' and age > 30;3. 查看岗位是teacher且薪资在9000-10000范围内的员工姓名、年龄、薪资
select name,age,salary from employeewhere post='teacher' and salary between 9000 and 10000;4. 查看岗位描述不为NULL的员工信息
select * from employee where not post_comment is null;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
select name,age,salary from employee where post='teacher' and salary in (10000,9000,30000);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
select name,age,salary from employee where post='teacher' and salary not in (10000,9000,30000);7. 查看岗位是teacher且名字是jin开头的员工姓名、年薪
select name,salary*12 from employee where post='teacher' and name like 'jin%';

#1、首先明确一点：分组发生在where之后，即分组是基于where之后得到的记录而进行的#2、分组指的是：将所有记录按照某个相同字段进行归类，比如针对员工信息表的职位分组，或者按照性别进行分组等#3、为何要分组呢？
    取每个部门的最高工资取每个部门的员工数取男人数和女人数小窍门：‘每’这个字后面的字段，就是我们分组的依据#4、大前提：可以按照任意字段分组，但是分组完毕后，比如group by post，只能查看post字段，如果想查看组内信息，需要借助于聚合函数

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

#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;

1. 查询岗位名以及岗位包含的所有员工名字
select post,group_concat(name) from employee group by post;2. 查询岗位名以及各岗位内包含的员工个数
select post,count(id) from employee group by post;3. 查询公司内男员工和女员工的个数
select sex,count(id) from employee group by sex;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
select sex,avg(salary) from employee group by sex;

#！！！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

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
select post,group_concat(name),count(id) from employee group by post having count(id) < 2;2. 查询各岗位平均薪资大于10000的岗位名、平均工资
select post,avg(salary) from employee group by post having avg(salary) > 10000;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
select post,avg(salary) from employee group by post having avg(salary) > 10000 and avg(salary) < 20000;

按单列排序SELECT * FROM employee ORDER BY salary;  #升序SELECT * FROM employee ORDER BY salary ASC;#升序SELECT * FROM employee ORDER BY salary DESC;  #降序

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 employeeORDER BY age,salary DESC;

#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select * from employee order by age asc,hire_date desc;
#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select post,avg(salary) from employee group by post having avg(salary)>10000 order by avg(salary) asc;
#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select post,avg(salary) from employee group by post having avg(salary)>10000 order by avg(salary) desc;

示例：SELECT * FROM employee ORDER BY salary DESC LIMIT 3;                    #默认初始位置为0
    SELECT * FROM employee ORDER BY salary DESCLIMIT 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 DESCLIMIT 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

SELECT * FROM employee WHERE name REGEXP '^ale';SELECT * FROM employee WHERE name REGEXP 'on$';SELECT * FROM employee WHERE name REGEXP 'm{2}';小结：对字符串匹配的方式
WHERE name = 'egon';
WHERE name LIKE 'yua%';
WHERE name REGEXP 'on$';