create database a;

use a;

create table employee(

empid varchar(10) primary key not null,

name varchar(10),

gender varchar(10),

title varchar(20),

birthday date,

depid varchar(10));

create table department(

depid varchar(10) primary key not null,

depname varchar(20));

create table salary(

empid varchar(10) primary key not null,

base_salary decimal(8,2),

title_salary decimal(8,2),

deduction int);

#修改表结构，在部门表中添加一个”部门简介”字段

alter table employee add 部门简介 varchar(100);

insert into employee values('1001','张三','男','高级工程师','1980-01-01','1111',null);

insert into employee values('1002','李四','女','助理工程师','1980-11-01','1111',null);

insert into employee values('1003','王五','男','工程师','1980-01-21','2222',null);

insert into employee values('1004','赵六','男','工程师','1980-01-11','2222',null);

insert into department(depid,depname) values

('1111','生产部'),

('2222','销售部'),

('3333','人事部');

insert into salary values

('1001',3200,1200,200),

('1002',4200,1100,100),

('1003',5200,2200,200),

('1004',2000,1500,150);

#5将李四的职称改为“工程师”，并将她的基本工资改为5700元，职务工资为1600。

update employee set title="工程师" where name="李四";

update salary set base_salary=5700,title_salary=600

where empid=(select empid from employee where name="李四");

#6查询出每个雇员的雇员编号，姓名，职称，所在部门，实发工资和应发工资。

#涉及employee表和salary表、department表

select employee.empid,name,title,depname,(base_salary+title_salary-deduction) as 实发工资,

(base_salary+title_salary) as 应发工资 from employee

left join salary on employee.empid=salary.empid

left join department on department.depid=employee.depid;

#7查询姓“张”且年龄小于40岁的员工的记录。

select * from employee where name like"张%" and (year(curdate())-year(birthday))<40;

#8查询销售部所有雇员的雇员编号，姓名，职称，部门名称，实发工资。

#涉及employee表和salary表、department表

select employee.empid,name,title,depname,

(base_salary+title_salary-deduction) as 实发工资 from employee

left join salary on employee.empid=salary.empid

left join department on department.depid=employee.depid where depname="销售部";

#9统计出各类职称的人数。

#按职称分组

select title,count(*)as 人数 from employee group by title;

#10.统计各部门的部门名称，实发工资总和，平均工资。

#涉及三张表及group by分组

select depname,sum(base_salary+title_salary-deduction)as 实发工资,

avg(base_salary+title_salary-deduction) as 平均工资 from employee

left join salary on employee.empid=salary.empid

left join department on department.depid=employee.depid group by depname;

select * from employee;

select * from salary;

select * from department;