145 lines
5.2 KiB
SQL
145 lines
5.2 KiB
SQL
drop database if exists hrs;
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create database hrs default charset utf8mb4;
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use hrs;
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create table tb_dept
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(
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dno int not null comment '编号',
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dname varchar(10) not null comment '名称',
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dloc varchar(20) not null comment '所在地',
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primary key (dno)
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);
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insert into tb_dept values
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(10, '会计部', '北京'),
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(20, '研发部', '成都'),
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(30, '销售部', '重庆'),
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(40, '运维部', '深圳');
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create table tb_emp
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(
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eno int not null comment '员工编号',
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ename varchar(20) not null comment '员工姓名',
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job varchar(20) not null comment '员工职位',
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mgr int comment '主管编号',
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sal int not null comment '员工月薪',
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comm int comment '每月补贴',
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dno int comment '所在部门编号',
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primary key (eno),
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foreign key (dno) references tb_dept (dno)
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);
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-- alter table tb_emp add constraint pk_emp_eno primary key (eno);
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-- alter table tb_emp add constraint uk_emp_ename unique (ename);
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-- alter table tb_emp add constraint fk_emp_mgr foreign key (mgr) references tb_emp (eno);
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-- alter table tb_emp add constraint fk_emp_dno foreign key (dno) references tb_dept (dno);
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insert into tb_emp values
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(7800, '张三丰', '总裁', null, 9000, 1200, 20),
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(2056, '乔峰', '分析师', 7800, 5000, 1500, 20),
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(3088, '李莫愁', '设计师', 2056, 3500, 800, 20),
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(3211, '张无忌', '程序员', 2056, 3200, null, 20),
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(3233, '丘处机', '程序员', 2056, 3400, null, 20),
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(3251, '张翠山', '程序员', 2056, 4000, null, 20),
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(5566, '宋远桥', '会计师', 7800, 4000, 1000, 10),
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(5234, '郭靖', '出纳', 5566, 2000, null, 10),
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(3344, '黄蓉', '销售主管', 7800, 3000, 800, 30),
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(1359, '胡一刀', '销售员', 3344, 1800, 200, 30),
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(4466, '苗人凤', '销售员', 3344, 2500, null, 30),
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(3244, '欧阳锋', '程序员', 3088, 3200, null, 20),
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(3577, '杨过', '会计', 5566, 2200, null, 10),
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(3588, '朱九真', '会计', 5566, 2500, null, 10);
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-- 查询月薪最高的员工姓名和月薪
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select ename, sal from tb_emp where sal=(select max(sal) from tb_emp);
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select ename, sal from tb_emp where sal>=all(select sal from tb_emp);
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-- 查询员工的姓名和年薪((月薪+补贴)*13)
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select ename, (sal+ifnull(comm,0))*13 as ann_sal from tb_emp order by ann_sal desc;
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-- 查询有员工的部门的编号和人数
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select dno, count(*) as total from tb_emp group by dno;
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-- 查询所有部门的名称和人数
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select dname, ifnull(total,0) as total from tb_dept left join
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(select dno, count(*) as total from tb_emp group by dno) tb_temp
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on tb_dept.dno=tb_temp.dno;
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-- 查询月薪最高的员工(Boss除外)的姓名和月薪
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select ename, sal from tb_emp where sal=(
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select max(sal) from tb_emp where mgr is not null
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);
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-- 查询月薪排第2名的员工的姓名和月薪
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select ename, sal from tb_emp where sal=(
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select distinct sal from tb_emp order by sal desc limit 1,1
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);
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select ename, sal from tb_emp where sal=(
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select max(sal) from tb_emp where sal<(select max(sal) from tb_emp)
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);
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-- 查询月薪超过平均月薪的员工的姓名和月薪
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select ename, sal from tb_emp where sal>(select avg(sal) from tb_emp);
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-- 查询月薪超过其所在部门平均月薪的员工的姓名、部门编号和月薪
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select ename, t1.dno, sal from tb_emp t1 inner join
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(select dno, avg(sal) as avg_sal from tb_emp group by dno) t2
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on t1.dno=t2.dno and sal>avg_sal;
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-- 查询部门中月薪最高的人姓名、月薪和所在部门名称
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select ename, sal, dname
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from tb_emp t1, tb_dept t2, (
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select dno, max(sal) as max_sal from tb_emp group by dno
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) t3 where t1.dno=t2.dno and t1.dno=t3.dno and sal=max_sal;
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-- 查询主管的姓名和职位
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-- 提示：尽量少用in/not in运算，尽量少用distinct操作
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-- 可以使用存在性判断（exists/not exists）替代集合运算和去重操作
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select ename, job from tb_emp where eno in (
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select distinct mgr from tb_emp where mgr is not null
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);
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select ename, job from tb_emp where eno=any(
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select distinct mgr from tb_emp where mgr is not null
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);
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select ename, job from tb_emp t1 where exists (
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select 'x' from tb_emp t2 where t1.eno=t2.mgr
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);
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-- MySQL8有窗口函数：row_number() / rank() / dense_rank()
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-- 查询月薪排名4~6名的员工的排名、姓名和月薪
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select ename, sal from tb_emp order by sal desc limit 3,3;
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select row_num, ename, sal from
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(select @a:=@a+1 as row_num, ename, sal
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from tb_emp, (select @a:=0) t1 order by sal desc) t2
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where row_num between 4 and 6;
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-- 窗口函数不适合业务数据库，只适合做离线数据分析
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select
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ename, sal,
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row_number() over (order by sal desc) as row_num,
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rank() over (order by sal desc) as ranking,
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dense_rank() over (order by sal desc) as dense_ranking
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from tb_emp limit 3 offset 3;
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select ename, sal, ranking from (
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select ename, sal, dense_rank() over (order by sal desc) as ranking from tb_emp
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) tb_temp where ranking between 4 and 6;
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-- 窗口函数主要用于解决TopN查询问题
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-- 查询每个部门月薪排前2名的员工姓名、月薪和部门编号
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select ename, sal, dno from (
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select ename, sal, dno, rank() over (partition by dno order by sal desc) as ranking
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from tb_emp
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) tb_temp where ranking<=2;
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select ename, sal, dno from tb_emp t1
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where (select count(*) from tb_emp t2 where t1.dno=t2.dno and t2.sal>t1.sal)<2
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order by dno asc, sal desc;
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