前言：以下試題中涉及的 table 均來自博主前面發的隨筆“【MySQL】筆記（1）--- MySQL 數據庫概述；常用 DOS命令，SQL命令（初步）；”
1.取得每個部門最高薪水的人員名稱
先取出每個部門的最高薪水，再作為臨時表與（對應最高薪水的人員名稱表）連接
select
e.ename,t.*
from
emp e
join
(select deptno,max(sal) as maxsal from emp group by deptno)t
on
t.deptno = e.deptno and t.maxsal = e.sal
2. 哪些人的薪水在部門的平均薪水之上
先取出每個部門的平均薪水，再作為臨時表與（薪水在其部門平均薪水上的部門名稱，薪水表）連接
select
t.*,e.ename,e.sal
from
emp e
join
(select deptno,avg(sal) as avgsal from emp group by deptno)t
on
e,deptno = t,deptno and e.sal > t.avgsal;
3.取得部門中所有人的平均薪水等級
找到每個人的薪水等級（emp連接salgrade）
select
e.ename,e.sal,e.deptno,s.grade
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal;
基於以上結果繼續按照deptno分組，求grade的平均值（直接兩張表就行，不需要臨時表）
select
e.deptno,avg(s.grade)
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal
group by
e.deptno;
4.不准用組函數（Max），取得最高薪水（給出兩種解決方案）
第一種，降序（limit）
select ename,sal from emp order by sal desc limit 1;
第二種方案，表的自連接
select sal from emp where sal not in(select distinct a.sal from emp a join emp b on a.sal<b.sal);
5.取出平均薪水最高的兩個部門編號（至少給出兩種解決方案）
第一種方案：
select deptno,avg(sal) as avgsal from emp group by deptno order by avgsal desc limit 1;
第二種解決方案：
select max(t.avgsal) from (select avg(sal) as avgsal from emp group by deptno) t;
select
deptno,avg(sal) as avgsal
from
emp
group by
deptno
having
avgsal = (select max(t.avgsal) from (select avg(sal) as avgsal from emp group by deptno) t);
6.求平均薪水的等級最低的部門的部門名稱
找出最低平均薪水對應的等級
select
grade
from
salgrade
where
(select avg(sal) as avgsal,deptno from emp order by avgsal asc limit 1) between losal and hisal;
找出（等於最低平均薪水的等級對應的）部門名稱，平均薪水，等級
select
t.*,s.grade
from
(select d.dname,avg(sal) as avgsal from emp e join dept on e.deptno = d.deptno group by d.dname) t
join
salgrade s
on
t.avgsal between s.losal and s.hisal;
where
s.grade = (select grade from salgrade where (select avg(sal) as avgsal,deptno from emp order by avgsal asc limit 1)
between losal and hisal);
7.取出比普通員工（員工代碼沒有在mgr字段出現的）的最高薪水還要高的領導人姓名
注意：not in 在使用時，后面小括號里記得排除 null
找到普通員工的最高薪水
select max(sal) from emp where empno not in(select distinct mgr from emp where mgr is not null);
找到高於（普通員工的最高薪水）的員工
select
ename,sal
from
emp
where
sal > (select max(sal)
from
emp
where
empno not in(select distinct mgr from emp where mgr is not null));
8.取出薪水最高的前五名
select ename,sal from emp order by sal desc limit 5;
9.取出薪水最高的第六到第十的員工
select ename,sal from emp order by sal desc limit 5,5;
10.取出最后入職的5名員工;
select ename,hiredate from emp order by hiredate desc limit 5;
11.取出每個薪水等級有多少個員工
select
s.grade,count(*)
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal
group by
s.grade;
12.列出所有員工及領導的名字
select
a.ename '員工',b.ename '領導'
from
emp a
left join
emp b
on
a.mgr = b.empno;
13.列出受雇日期早於直接上級的所有員工的姓名，受雇日期，直接上級的姓名，受雇日期,部門名稱
select
a.empno '員工',a.hiredate,b.ename '領導',b.hire date,d.dname
from
emp a
join
emp b
on
a.mgr = b.empno
join
dept d
on
a.deptno = d.deptno
where
a.hiredate < b.hiredate;
14.列出部門名稱和這些部門的員工信息，同時列出那些沒有員工的部門
select
e.*,d.dname
from
emp e
right join
dept d
on
e.deptno = d.deptno;
15.列出至少有5個員工的所有部門
select
deptno
from
emp
group by
deptno
having
count(*) >= 5;
16.列出薪水比“SMITH”多的所有員工
select
ename,sal
from
emp
where
sal > (select sal from emp where ename = 'SMITH');
17.列出最低薪水大於1500的各種工作及其從事此工作的全部雇員人數
select
job,count(*)
from
emp
group by
job
having
min(sal) > 1500;
18.列出在部門“SALES”<銷售部>工作的員工的姓名，假定不知道銷售部的部門編號
select
ename
from
emp
where
deptno = (select deptno from dept where dname = 'SALES');
19.列出薪水高於公司平均薪水的所有員工，所在部門，上級領導，雇員的工資等級
select
e.ename '員工',d.dname,l.ename '領導',s.grade
from
emp e
join
dept d
on
e.empno = d.deptno
left join
emp l
on
e.mgr = l.empno
join
salgrade s
on
e.sal between s.losal and s.hisal
where
e.sal > (select avg(sal) from emp);
20.列出與“SCOTT”從事相同工作的所有員工及其部門名稱
select
e.ename,e.job,d.dname
from
emp e
join
dept d
on
e.deptno = d.deptno
where
e.job = (select job from emp where ename = 'SCOTT')
and e.name <> 'SCOTT';
21.列出薪水等於部門30中員工的薪水的其他員工的姓名和薪水
select
ename,sal
from
emp
where
sal in(select distinct sal from emp where deptno = 30)
and
deptno <> 30;
22.列出薪水高於在部門30工作的所有員工的薪水的員工姓名和薪水，部門名稱
select
e.ename,e.sal,d.dname
from
emp e
join
dept d
on
e.deptno = d,deptno
where
e.sal > (select max(sal) from emp where deptno = 30) ;
23.列出在每個部門工作的員工數量，平均工資和平均服務期限
select
d.deptno,
count(e.ename) as ecount,
ifnull(avg(e.sal),0) as avgsal,
ifnull(avg(timestampdiff(YEAR,hiredate,now())),0) as avgtime
from
emp e
right join
dept d
on
e.deptno = d.deptno
group by
d.deptno;
計算兩個時間間隔的函數，語法為：
timestampdiff(間隔類型,前一個日期,后一個日期)
返回日期間的整數差。
FRAC_SECOND 表示間隔是毫秒
SECOND 秒
MINUTE 分鍾
HOUR 小時
DAY 天
WEEK 星期
MONTH 月
QUARTER 季度
YEAR 年
24.列出所有員工的姓名，部門名稱，和薪水
select
e.ename,d.dname,e.sal
from
emp e
join
dept d
on
e.deptno = d.deptno;
25.列出所有部門的詳細信息和人數
select
d.deptno,d.dname,d.loc,count(e.ename)
from
emp e
join
dept d
on
e.deptno = d.deptno
group by
d.deptno,d.name,d.loc;
26.列出各種工作的最低工資及從事此工作的雇員姓名
select
e.ename,t.*
from
emp e
join
(select job,min(sal) as minsal from emp group by job)t
on
e.job = t.job and e.sal = t.,minsal;
27.列出各個部門MANAGER（領導）的最低薪水
select
deptno,min(sal)
from
emp
where
job = 'MANAGER'
group by
deptno;
28.列出所有員工的年工資，按年薪從低到高排序
select
ename,(sal + ifnull(comm,0))*12 as yearsal
from
emp
order by
yearsal asc;
29.求出員工領導薪水超過3000的員工名稱和領導
select
a.ename '員工',b.ename '領導'
from
emp a
join
emp b
on
a.mgr = b.empno
where
b.sal > 3000;
30.求出部門名稱帶’S‘的部門員工的工資合計，部門人數
select
d.deptno,d.dname,d.loc,count(e.ename),ifnull(sum(e.sal),0) as sumsal
from
emp e
right join
dept d
on
e.deptno = d.deptno
where
d.dname like '%S%'
group by
d.deptno,d.name,d.loc;
31.給任職日期超過30年的員工加薪 10%
update
emp
set
sal= sal*1.1 where timestampdiff(YEAR,hiredate,now())>30;
試題出處：https://www.bilibili.com/video/BV1fx411X7BD?p=1
ps：博主少寫了3道喲！ ( •̀ ω •́ )✧