MySQL基础试题训练

1.前言需要自己手动创建数据库

2.提前准备：建表语句

use day0202;
-- 部门表
create table dept(
	deptno int primary key auto_increment, -- 部门编号
	dname varchar(14) ,	  -- 部门名字
	loc varchar(13)   -- 地址
) ;
-- 员工表
create table emp(
	empno int primary key auto_increment,-- 员工编号
	ename varchar(10), -- 员工姓名										-
	job varchar(9),	-- 岗位
	mgr int,	 -- 直接领导编号
	hiredate date, -- 雇佣日期，入职日期
	sal int, -- 薪水
	comm int,  -- 提成
	deptno int not null, -- 部门编号
	foreign key (deptno) references dept(deptno)
);
insert into dept values(10,'财务部','北京');
insert into dept values(20,'研发部','上海');
insert into dept values(30,'销售部','广州');
insert into dept values(40,'行政部','深圳');
insert into emp values(7369,'刘一','职员',7902,'1980-12-17',800,null,20);
insert into emp values(7499,'陈二','推销员',7698,'1981-02-20',1600,300,30);
insert into emp values(7521,'张三','推销员',7698,'1981-02-22',1250,500,30);
insert into emp values(7566,'李四','经理',7839,'1981-04-02',2975,null,20);
insert into emp values(7654,'王五','推销员',7698,'1981-09-28',1250,1400,30);
insert into emp values(7698,'赵六','经理',7839,'1981-05-01',2850,null,30);
insert into emp values(7782,'孙七','经理',7839,'1981-06-09',2450,null,10);
insert into emp values(7788,'周八','分析师',7566,'1987-06-13',3000,null,20);
insert into emp values(7839,'吴九','总裁',null,'1981-11-17',5000,null,10);
insert into emp values(7844,'郑十','推销员',7698,'1981-09-08',1500,0,30);
insert into emp values(7876,'郭靖','职员',7788,'1987-06-13',1100,null,20);
insert into emp values(7900,'令狐冲','职员',7698,'1981-12-03',950,null,30);
insert into emp values(7902,'张无忌','分析师',7566,'1981-12-03',3000,null,20);
insert into emp values(7934,'杨过','职员',7782,'1983-01-23',1300,null,10);

3.具体需求与答案，自己训练最好把答案删除自行训练

use day0202;
-- 1．列出至少有一个员工的所有部门。
#查询所有的部门总数大于1的部门；
select deptno from emp group by deptno having count(deptno)>1;
#查询对应的部门名称
select dname from dept emp where deptno in (select deptno from emp group by deptno having count(deptno)>1);

-- 2．列出薪金比"刘一"多的所有员工。
#查询刘一的薪资
select sal from emp where ename="刘一";
select * from emp where sal>(select sal from emp where ename="刘一");

-- 3．***** 列出所有员工的姓名及其直接上级的姓名。
#思路：先查看对应的员工id与上级id
select empno,mgr from emp ;
#查询员工姓名查询上级的id
select emp.ename as 上司 , e.ename as 员工 from  emp, (select empno,mgr,ename from emp ) as e where emp.empno =e.mgr;
#思路反思：
#1.根据员工表查询员工的id上司的id 姓名
#2.建立条件让找到上司id对应的员工
#精简答案
select e1.ename,e2.ename from emp as e1,emp as e2
where e1.mgr=e2.empno;

-- 4．列出受雇日期早于其直接上级的所有员工。
select e1.ename,e2.ename from emp as e1 inner join emp as e2 on e1.empno=e2.mgr;

select e2.* from emp as e1 inner join emp as e2 on e1.empno=e2.mgr where e1.hiredate<e2.hiredate;
-- 5．列出部门名称和这些部门的员工信息，同时列出那些没有员工的部门。
select * from dept as d left join emp as e on d.deptno=e.deptno
-- 6．列出所有job为“职员”的姓名及其部门名称。
select e.ename ,d.dname from emp as e inner join dept as d on d.deptno=e.deptno where job="职员";
-- 7．列出最低薪金大于1500的各种工作。
select job from emp  group by job having  min(sal)>1500;
-- 8．列出在部门 "销售部" 工作的员工的姓名，假定不知道销售部的部门编号。
select deptno from dept where dname ="销售部";
select ename as 姓名 ,empno as 编号 from emp where deptno in (select deptno from dept where dname ="销售部");
-- 9．列出薪金高于公司平均薪金的所有员工。
select avg(sal) from emp ;
select * from emp where sal>(select avg(sal) from emp);
-- 10．列出与"周八"从事相同工作的所有员工。
#创建driver Manger的注册驱动
#使用connection创建连接urlusernamepassword
#向数据库发送sql语句
#
select job from emp where ename="周八";
select * from emp where job in (select job from emp where ename="周八");
-- 11．列出薪金等于部门30中员工的薪金的所有员工的姓名和薪金。
select ename , sal from emp  where deptno=30;
-- 12．列出薪金高于在部门30工作的所有员工的薪金的员工姓名和薪金。
select max(sal) from emp where deptno =30; 
select ename ,sal from emp where sal>(select max(sal) from emp where deptno =30);
-- 13．列出在每个部门工作的员工数量、平均工资。
select count(deptno) ,avg(sal) from emp group by deptno having avg(sal);
-- 14．列出所有员工的姓名、部门名称和工资。
select e.ename,d.dname,e.sal from emp as e inner join dept as d on e.deptno=d.deptno ;
-- 15．列出所有部门的详细信息和部门人数。
select deptno, count(deptno) from emp group by deptno having count(deptno);
select d.*,e.c from dept as d left join (select deptno as dd, count(deptno) as c from emp group by deptno having count(deptno))as e on d.deptno=e.dd;
-- 16．列出各种工作的最低工资。
select job,min(sal) from emp group by job having min(sal); 
-- 17．列出各个部门的 经理 的最低薪金。
select deptno ,min(sal) from emp where job = "经理" group by deptno;
select*  from dept inner join (select deptno ,min(sal) from emp where job = "经理" group by deptno)as e on e.deptno =dept.deptno;
-- 18．列出所有员工的年工资,按年薪从低到高排序。 
select * ,sal*12+IFNULL(comm,0)*12 as 年薪 from emp ;
-- 19.查出emp表中薪水在3000以上（包括3000）的所有员工的员工号、姓名、薪水。
select empno , ename ,sal from emp where sal >=3000;
-- 20.查询出所有薪水在'陈二'之上的所有人员信息。
select sal from emp where ename ="陈二";
select * from emp where sal>(select sal from emp where ename ="陈二");
-- 21.查询出emp表中部门编号为20，薪水在2000以上（不包括2000）的所有员工，显示他们的员工号，姓名以及薪水，以如下列名显示：员工编号 员工名字 薪水
select * from emp where deptno=20 and sal>2000;
-- 22.查询出emp表中所有的工作种类（无重复）
select DISTINCT job from emp;
-- 23.查询出所有奖金（comm）字段不为空的人员的所有信息。
select * from emp where comm  is not null;
-- 24.查询出薪水在800到2500之间（闭区间）所有员工的信息。（注：使用两种方式实现and以及between and）
select * from emp where sal between 800 and 2500;
select * from emp where sal>=800 and sal<2500;
-- 25.查询出员工号为7521，7900，7782的所有员工的信息。（注：使用两种方式实现，or以及in）
select * from emp where empno in (7521,7900,7782);
select * from emp where empno  =7521 or empno=7900 or empno=7782;
-- 26.查询出名字中有“张”字符，并且薪水在1000以上（不包括1000）的所有员工信息。
select * from emp where ename like "%张%" and sal>1000;
-- 27.查询出名字第三个汉字是“忌”的所有员工信息。
select * from emp where ename like "__忌";
-- 28.将所有员工按薪水升序排序，薪水相同的按照入职时间降序排序。
select * from emp  ORDER BY sal asc ,hiredate desc;
-- 29.将所有员工按照名字首字母升序排序，首字母相同的按照薪水降序排序。 order by convert(name using gbk) asc; 
select * from emp order by convert(ename USING gbk) asc ,sal desc;
-- 30.查询出最早工作的那个人的名字、入职时间和薪水。
select min(hiredate) from emp;
select ename ,hiredate ,sal from emp where hiredate in(select min(hiredate) from emp);
-- 31.显示所有员工的名字、薪水、奖金，如果没有奖金，暂时显示100.
#不会写，判断为空加100
select ename ,sal ,comm+100 from emp  where comm if null ;


select ename,sal,ifnull(comm,100)
from emp;


-- 32.显示出薪水最高人的职位。
select  max(sal) from emp; 
select job ,ename from emp  where sal in(select  max(sal) from emp);
-- 33.查出emp表中所有部门的最高薪水和最低薪水，部门编号为10的部门不显示。
select deptno,  min(sal), max(sal) from emp group by deptno HAVING deptno<> 10 ;
-- 34.删除10号部门薪水最高的员工。
select max(sal)  from emp where deptno=10;
select empno from emp where sal=(select max(sal)  from emp where deptno=10);
delete from emp where empno=(select empno from emp where sal=(select max(sal)  from emp where deptno=10));


#标准答案
select empno from emp
where deptno=10 and sal>=all(select sal from emp where deptno=10);

delete from emp 
where empno = (select empno from (select empno from emp
				where deptno=10 
					and sal>=all(select sal from emp where deptno=10))  as temp);

-- 35.将薪水最高的员工的薪水降30%。
select max(sal)*(1-0.3) from emp ;

select empno from emp 
where sal >= all(select sal from emp);

update emp 
set sal=sal*(1-0.3)
where empno in (select temp.empno from (select empno from emp 
				where sal >= all(select sal from emp)) temp);


select * from emp;
-- 36.查询员工姓名，工资和 工资级别(工资>=3000 为3级，工资>2000 为2级，工资<=2000 为1级)
-- 语法：case when ... then ... when ... then ... else ... end
select ename ,sal,
case when sal>3000 then "3级"
			when sal>2000 then "2级"
			else "1级"
			end
			from emp;

select ename,
	case when sal>3000 then '3级' 
		 when sal>2000 then '2级'
		 else '1级'
	end
from emp;