数据库习题

show databases;
CREATE DATABASE HR CHARSET UTF8;
USE HR;
CREATE TABLE TbDept(deptno tinyint primary key,dname varchar(30) not null,dloc varchar(30) not null);

create table TbEmp(empno int primary key,ename varchar(20) not null,job varchar(20) not null,mgr int,sal int not null,dno tinyint);
alter table TbEmp add constraint fk_dno FOREIGN key(dno) references TbDept(deptno);

insert into TbDept  VALUES('10','会计部','北京');
insert into TbDept  values('20','研发部','成都');
insert into TbDept  values('30','销售部','重庆');
insert into TbDept  values('40','运维部','深圳');
select * from TbDept;

insert into TbEmp  values(7800,'张三丰','总裁',null,9000,20);
insert into TbEmp  values(2056,'乔峰','分析师',7800,5000,20);
insert into TbEmp  values(3088,'李莫愁','设计师',2056,3500,20);
insert into TbEmp  values(3211,'张无忌','程序员',2056,3200,20);
insert into TbEmp  values(3233,'丘处机','程序员',2056,3400,20);
insert into TbEmp  values(3251,'张翠山','程序员',2056,4000,20);
insert into TbEmp  values(5566,'宋明月','会计师',7800,4000,10);
insert into TbEmp  values(5234,'郭靖','出纳',5566,2000,10);
insert into TbEmp  values(3344,'黄蓉','销售主管',7800,3000,10);
insert into TbEmp  values(1359,'胡一刀','销售员',3344,1800,30);
insert into TbEmp  values(4466,'苗人凤','销售员',3088,3200,30);
insert into TbEmp  values(3244,'欧阳锋','程序员',3088,3200,20);
insert into TbEmp  values(3577,'杨过','会计师',5566,2200,10);
insert into TbEmp  values(3588,'朱九真','会计师',5566,2200,10);
update TbEmp set dno=30 where job='销售主管';
select * from TbEmp;

1.select sal,ename from TbEmp where sal = (SELECT max(sal) from TbEmp);
-- select sal,ename from(select max(sal) s from TbEmp) t1 join TbEmp t2 on t1.s=t2.sal;
2.select ename,sal * 10 from TbEmp;
3.select count(*) ,d.deptno,d.dname from TbEmp e join TbDept d on e.dno=d.deptno GROUP BY d.deptno;
4.SELECT t1.deptno,t1.dname,IFNULL(t2.c,0) from TbDept t1 left join (SELECT dno,count(*) as c from TbEmp GROUP BY dno) t2 on t1.deptno=t2.dno;
-- 左连接
5.-- select sal,ename from (select max(sal) s FROM TbEmp where empno not in (7800)) t1 join TbEmp t2 on t1.s=t2.sal ;
select sal,ename from TbEmp t1 where t1.sal=(select max(sal) s from TbEmp t where empno not in (7800));
6.-- select sal,ename,empno from (select avg(sal) s from TbEmp) t1 join TbEmp t2 on t1.s<t2.sal;
select sal,ename,empno from TbEmp t where t.sal>(select avg(sal) s from TbEmp);
7.select * from TbDept t3 join(
select t1.dno,ename,sal from TbEmp t1 
join(
select avg(sal) as avgsal,dno from TbEmp GROUP BY dno) t2 
on t1.dno=t2.dno and t1.sal>avgsal) t4 
on t3.deptno=t4.dno;
8.select * from TbDept t3
join(
select ename,t1.dno,sal from TbEmp t1 
join(
select max(sal) as maxsal,dno from TbEmp GROUP BY dno) t2
on t1.dno=t2.dno and t1.sal=maxsal) as t4
on t3.deptno=t4.dno
9.SELECT * from TbEmp where empno in (SELECT distinct mgr from TbEmp where mgr is not null)
-- distinct 去重
10.select * from TbEmp ORDER BY sal LIMIT 3;
11.SELECT * from TbEmp ORDER BY sal LIMIT 5 offset 3;