多表练习题
create table dept(dept1 int(10),
dept_name char(20)
) default charset=utf8;
insert into dept values (101,'财务');
insert into dept values (102,'销售');
insert into dept values (103,'IT技术');
insert into dept values (104,'行政');
SELECT * fromdept;
create table emp(
sid intprimary key, -- 员工编号
namevarchar(10), -- 员工姓名
age int, -- 员工年龄
worktime_start date, -- 入职时间
incoming double, -- 收入
dept2 int,-- 部门号
foreign key (dept2) references dept(dept2)) defaultcharset=utf8;-- 关联dept表
-- alter table emp add foreign key (deptno) references dept(deptno);
insert into emp values(1789,'张三',35,"1980-01-01",4000,101);
insert into emp values(1674,'李四',32,'1983-04-01',3500,101);
insert into emp values(1776,'王五',24,'1990-07-01',2000,101);
insert into emp values(1568,'赵六',57,'1970-10-11',7500,102);
insert into emp values(1564,'荣七',64,'1963-10-11',8500,102);
insert into emp values(1879,'牛八',55,'1971-10-20',7300,103);
select * from emp;
1.列出每个部门的平均收入及部门名称;
核心词汇：emp、incoming 、 deptdept_name 、avg 、group by、
selectavg(incoming ),dept_name from dept inner joinempondept.dept1=emp.dept2.
方法一：selectavg(incoming ),dept_name from (select * from dept left joinempondept.dept1=emp.dept2)c group by dept_name;
方法二：select avg(incoming),dept_name from dept leftJOIN emp on dept.dept1=emp.dept2 GROUP BY dept_name ;
2.财务部门的收入总和；
dept "财务"
emp incoming
sum
selectsum(incoming ),dept_name from dept inner joinempondept.dept1=emp.dept2where dept_name="财务" ;
方法一：select sum(incoming) from (select *fromdept,emp where dept.dept1=emp.dept2)c where dept_name='财务';
方法二：selectsum(incoming ) from dept inner joinempondept.dept1=emp.dept2where dept_name="财务" ;
方法三：select sum(incoming) fromemp where dept2=(selectdept1fromdeptwheredept_name="财务");
3.It技术部入职员工的员工号
emp sid
dept it技术部门
name ，sid
方法一：select emp.sid from dept inner join emp on dept.dept1=emp.dept2 where dept_name="IT技术 ";
方法二：select sid from (select * from dept,emp where dept.dept1=emp.dept2)c where dept_name='IT技术';
方法三：selectsidfromempwhere dept2=(selectdept1fromdept where dept_name="IT技术") ;
方法四：selectsid fromdept,empwhere dept1=dept2anddept_name="IT技术" ;
4.财务部门收入超过2000元的员工姓名
emp incoming>2000
dept财务
方法一：SELECT name,incoming FROM Dept INNER JOIN Emp on Dept1=DEPT2 WHERE incoming>2000 AND Dept_name="财务";
方法二：SELECT emp.name fromempwhere dept2=(select dept1 from dept where dept_name='财务') and incoming>2000;
方法三：select name from (select * from dept,emp where dept.dept1=emp.dept2)c where incoming>2000 and dept_name= '财务';
方法四：select name from (select*from dept inner join emp on dept1=dept2 where incoming>2000)s where dept_name='财务'
5.找出销售部收入最低的员工的入职时间；
emp
dept
max
方法一：select woektime_start FROM emp INNER JOIN dept on dept.dept1=emp.dept2 whereincoming =(select min(incoming) from emp INNER JOIN dept on emp.dept2=dept.dept1 where dept.dept_name="销售")and dept_name="销售";
方二：（这种方法可以，弊端在与有重复的数据，只显示一条）
selecta.dept_name,b.sid,b.name,b.woektime_startfrom dept ajoin emp b ona.dept1 =b.dept2 where a.dept_name = "销售"ORDER BY b.incoming asc LIMIT 1;
6.找出年龄小于平均年龄的员工的姓名，ID和部门名称
思路：条件n：ame，sid ，dept_name
方法一:SELECT name,sid,dept_name FROM emp INNER JOIN dept ON dept.dept1 = emp.dept2 where age< (SELECT AVG(age) FROM emp);
方法二：
select sid,name,dept_name from (select * from emp,dept where dept1=dept2)s where age<(select avg(age)from emp);
7.列出每个部门收入总和高于9000的部门名称
条件： groupby dept_name
sum (incoming) >9000
结果：dept_name
方法一：
select s.dept_name from (select a.dept_name,sum(b.incoming) as k from dept a join emp b on a.dept1 = b.dept2GROUP BYa.dept_name HAVING k >9000)s;
方法二：
SELECT dept_name FROM dept INNER JOIN emp on dept.dept1=emp.dept2GROUP BY dept_name having sum(incoming)>90000;
方法三：
SELECT dept_name FROM
( SELECT sum( incoming ) a, dept_name FROM emp INNER JOIN dept ON dept.dept1 = emp.dept2 GROUP BY dept_name ) b
WHERE a > 9000;
方法四：SELECT dept_name from (SELECT sum(incoming) as s,dept2 from emp GROUP BY dept2 having s>9000)t1on dept.dept1=t1.dept2;
8.查出财务部门工资少于3800元的员工姓名
dept_name =财务 dept
incoming<3800 emp
name
方法一：
SELECT name FROM dept INNER JOIN emp on dept.dept1=emp.dept2where incoming<3800and dept_name="财务";
方法二：
select name from emp where incoming<3800 anddept2=(SELECT dept1 from dept WHERE dept_name='财务');
方法三
select name from (select*from dept,emp where dept1=dept2)s where incoming<3800 and dept_name="财务"
9.求财务部门最低工资的员工姓名；
条件
min
dept表 dept_name=财务
emp 表 min（ incoming ）
结果：员工姓名name
方法一：
select namefrom dept inner join emp on dept.dept1=emp.dept2 where
dept2=(select dept1 from dept where dept_name="财务" ) and incoming=(select min(incoming) from emp ,dept where emp.dept2=dept.dept1 anddept_name="财务");
方法二：
selectnamefrom emp ,deptwheredept1=dept2anddept_name="财务"ORDER BY incoming ascLIMIT 1
10.找出销售部门中年纪最大的员工的姓名
条件：dept表 dept_name="销售"
emp max（age）
结果：name
方法一:select name "姓名", age "年龄" from dept,emp where dept.dept1=emp.dept2 and
age=(select max(age) from dept,emp where dept.dept1=emp.dept2 and dept_name="销售")and dept_name="销售";
方法二：（缺陷是多个同样数据就显示一个）
SELECT name,agefrom emp INNER JOIN dept on emp.dept2=dept.dept1WHERE dept_name="销售"ORDER BYagedescLIMIT 0,1;
11.求收入最低的员工姓名及所属部门名称：
条件：emp min（incoming ）
结果：name，dept_name
方法一：
SELECT NAME,dept_name FROM dept inner joinempondept.dept1=emp.dept2 WHERE incoming=(SELECT MIN(incoming) FROM emp );
方法二：
SELECT name ,dept_name FROM(SELECT * FROM emp INNER JOIN dept ON dept.dept1 = emp.dept2)a WHERE incoming =( SELECT MIN(incoming) FROM emp);
方法三：SELECT name,dept_name fromemp left join dept on emp.dept2=dept.dept1 where incoming=(SELECT min(incoming) from emp left join dept on emp.dept2=dept.dept1);
12.求李四的收入及部门名称
条件：emp name=“李四”
结果：incoming dept_name
方法一：
SELECT incoming,dept_name FROM dept INNER JOIN emp on dept.dept1=emp.dept2where name="李四"
方法二：
select name,dept_name from(select * from dept,emp where dept.dept1=emp.dept2)c where name='李四';
方法三：select incoming,dept_name from (select*from dept,emp where dept1=dept2)s where name="李四";
13.求员工收入小于4000元的员工部门编号及其部门名称
条件：
emp incoming<4000
结果：dept1 ,deptname
方法一：select dept1,dept_name from(select * from dept,emp where dept.dept1=emp.dept2)cwhere incoming<4000;
方法二：select dept1,dept_name from emp left join dept on emp.dept2=dept.dept1 where incoming<4000;
方法三：
select dept1,dept_name from deptwheredept1 in (selectdept2fromempwhereincoming<4000) ;
14.列出每个部门中收入最高的员工姓名，部门名称，收入，并按照收入降序；
方法一：（缺陷：重复就显示一个）
SELECT name "姓名",incoming "收入",dept_name"部门" from(select * from dept,emp where dept.dept1=emp.dept2 order by incoming desc) b group bydept_nameORDER BYincoming desc;
方法二：
SELECT name "姓名",incoming "收入",dept_name"部门" from (select * from dept,emp where dept.dept1=emp.dept2)a where
(a. incoming ,a.dept_name )in (select max(incoming),dept_name from dept,emp where dept.dept1=emp.dept2 group by dept_nameorder by incoming desc) order by incoming desc;
方法三:
selectb.name,a.dept_name, b.incomingfrom(select max(incoming) as c,dept_name from dept, empwheredept1=dept2 groupby dept_name)a LEFT JOIN ( select* fromemp ,deptwheredept1=dept2)bona.dept_name=b.dept_nameanda.c =b.incoming orderbyb.incoming desc;
15.求出财务部门收益最高的俩位员工的姓名，工号，收益
条件： dept dept_name="财务" max（incoming） limit 2
结果 ：emp name sid incoming
方法一：select name,sid,incoming from emp inner join dept on dept1=dept2 where dept_name='财务' order by incoming desc limit 2;
方法二：select * from (select name,sid,incoming from dept left join emp on dept.dept1=emp.dept2 where dept_name="财务" order by incoming desc)as s where sid limit 0,2
方法三: select a.dept1,a.dept_name,b.name,b.incoming from dept a ,emp b wherea.dept1 = b.dept2and a.dept_name ='财务'ORDER BYb.incoming desc LIMIT 2;
16.查询财务部低于平均收入的员工号与员工姓名：（按所有的平均薪资）
条件： dept dept_name=“财务” avg（incoming） >
结果：sid name
方法一：
select sid,name fromempwhere incoming<(select avg(incoming)from emp) and dept2=(select dept1 from dept where dept_name='财务');
方法二：
SELECT sid,name FROM dept INNER JOIN emp on dept.dept1=emp.dept2 WHERE incoming<(SELECT avg(incoming) FROM emp)and dept_name="财务";
备注（在多表中求得平均值）SELECT sid,name fromemp left join dept on emp.dept2=dept.dept1 where dept_name="财务" and incoming<(SELECT avg(incoming) from emp left join dept on emp.dept2=dept.dept1)
方法三：
select sid,namefrom (select * from dept,emp where dept.dept1=emp.dept2)cwhere incoming<(select avg(incoming) from emp) and dept_name='财务';
17.列出部门员工数大于1个的部门名称；
条件：dept count（name）
结果：dept_name
方法一：select dept_name from dept where dept1 in(select dept2 from emp group by dept2 having count(dept2)>1)
方法二：SELECT DISTINCT(dept_name) FROM empINNER JOIN dept ON emp.dept2 = dept.dept1WHERE (SELECT count(name) from emp)>1;
方法三：SELECT dept_name from(SELECTdept_name,count(name)s fromdept INNER JOIN emp on dept1=dept2 GROUP BY dept_name having s>1)d
18.列出部门员工收入不超过7500，且大于3000的员工年纪及部门编号；
条件：emp incoming<=750 and incoming>3000
结果：age ,dept_name
方法一：select age, dept2 from emp where incoming >3000 and incoming<=7500;
方法二：
select age,dept2from (select * from dept,emp where dept.dept1=emp.dept2)cwhere 7500>=incoming and incoming>3000;
方法三：SELECT name,age,dept1FROMdept inner JOIN emp on dept.dept1=emp.dept2 WHERE incoming BETWEEN 3000 and 7500andincoming!=3000;
错误写法：
SELECT name,age,dept1FROM dept inner JOIN emp on dept.dept1=emp.dept2 WHERE incoming BETWEEN 3000 and 7500;（包含3000了）
19.求入职于20世纪70年代的员工所属部门名称；
条件：20世纪 表示1900-1999内， 70年代 ：大于等于1970~小于1980 woerktime =“197%”
结果： dept dept_name
方法一：select dept_name from emp left join dept on emp.dept2=dept.dept1 wherewoektime_start >="19700101" and woektime_start<"19800101";
方法二：SELECT name,dept_name FROMdept RIGHT JOIN emp on dept.dept1=emp.dept2WHERE worktime BETWEEN "1970-01-01" and "1979-12-31";
方法三：select dept_name "部门"from dept,emp wheredept.dept1=emp.dept2 andwoektime_start like "197%" ;
方法四：select dept_name from emp inner join dept on dept1=dept2 wherewoektime_start >="19700101" and woektime_start<="19791231";
20.查找张三所在的部门名称；
条件： emp name=“张三”
结果：dept dept_name
方法一：
select dept_name from emp inner join dept on dept1=dept2 where name='张三';
方法二：
select dept_name from dept where dept1=(select dept2 from emp where name='张三');
方法三：
select dept_name "部门" from dept,emp where dept2=dept1 and name="张三";
21.列出每一个部门中年纪最大的员工姓名，部门名称；
条件：group by dept_name max(age)
结果：name，dept_name
方法一：sel ect name "姓名",dept_name "部门名" from dept,emp where dept1=dept2 and
(dept_name,age) in (select dept_name,max(age) from dept,emp where dept1=dept2 group by dept_name )；
方法二：
selectb.name,a.dept_name, b.incomingfrom(select max(age) as c,dept_name from dept, empwheredept1=dept2 groupby dept_name)a LEFT JOIN ( select* fromemp ,deptwheredept1=dept2)bona.dept_name=b.dept_nameanda.c =b.age
方法三：（是一种方法，当出现多条相同数据，就显示一条）
select name,dept_name from (select * from emp inner join dept on dept.dept1=emp.dept2 order by age desc) a group by dept_name ;
22.列出每一个部门的员工总收入及部门名称；
条件: groupby dept_name
结果;sum(incoming) dept_name
方法一：SELECT sum(incoming),dept_name FROMdept leftJOIN emp on dept.dept1=emp.dept2 GROUP BY dept_name
方法二：select sum(incoming),dept_name from dept left join emp on dept.dept1=emp.dept2 group by dept1;
方法三：（不合理的写法，答案正确）
SELECT sum(incoming),dept_name FROM dept iNNER JOIN emp on dept.dept1=emp.dept2 WHERE (SELECT sum(incoming) FROM emp ) GROUP by dept_name;
方法四：select dept_name,sum(incoming)from (select * from dept,emp where dept.dept1=emp.dept2)cgroup by dept_name；
23.列出部门员工收入大于7000的员工号，部门名称；
条件： dept dept_name
emp incoming>7000 sid
结果： sid dept_name
方法一：SELECT sid,dept_name FROM dept left JOIN emp on dept1=dept2 where incoming>7000
方法二：select a.sid,a.dept_name from(select * from emp inner join dept on emp.dept2=dept.dept1 where incoming>7000) a;
方法三：
select sid,dept_namefrom (select * from dept,emp where dept.dept1=emp.dept2)c where incoming>7000;
24.找出哪个部门还没有员工入职；
条件：dept_name name或sid 判断
结果：dept_name
方法一：
select dept_namefrom dept left join emp on dept.dept1=emp.dept2 group by dept1 having (count(sid)=0)
方法二：select * from dept where dept1 not in ( select dept2 from emp);
方法三：select dept_name fromemp right join dept on dept1=dept2 where name is null;
方法四：
select dept_name from dept left join emp on dept.dept1=emp.dept2where name is NULL;
方法五：SELECT dept_name FROM (SELECT * FROM emp RIGHT JOIN dept ON emp.dept2 = dept.dept1)a WHEREsid is NULL;
25.先按部门号大小排序，再依据入职时间由早到晚排序员工信息表 ；
条件：二次排序 orderby desc从大到小 早到晚asc
结果：所有信息
方法一：
SELECT * fromdept left join emp on dept.dept1=emp.dept2 ORDER BY dept1 desc,woektime_start asc ;
方法二：（部门编号104不显示，内连接方法）
select * fromdept a ,emp b where a.dept1 = b.dept2 ORDER BYa.dept1 desc,b.woektime_start asc;
方法三：SELECT * from empORDER BY dept2 DESC ,woektime_start asc;
26.求出财务部门工资最高员工的姓名和员工号
条件： dept_name ="财务" max（incoming）
结果：name，sid
方法一：SELECT name,sidfrom dept left join emp on dept.dept1=emp.dept2 where incoming=(SELECT max(incoming) from dept left join emp on dept.dept1=emp.dept2 where dept_name="财务")and dept_name="财务" ;
方法 二：
select name, sid from emp inner join dept on dept1= dept2 where dept_name='财务' order by incoming desc limit 1
方法三：SELECT name,sid FROM dept,emp WHERE dept.dept1=emp.dept2 AND (SELECT max(incoming) from (SELECT incoming from dept a ,emp b where a.dept1=b.dept2 and dept_name="财务")s )=incominganddept_name="财务";
方法四：（缺陷有重复数据）
select name,sid FROM dept d INNER JOIN emp e on d.dept1=e.dept2 WHERE dept_name="财务" AND incoming in(SELECT MAX(incoming) FROM emp GROUP BY dept2);#
方法五：
SELECT name,dept1FROM emp INNER JOIN dept ON emp.dept2 = dept.dept1 WHERE dept_name='财务'ORDER BY incoming DESCLIMIT 0,1;
27.求出工资在7500到8500之间，年龄最大的员工的姓名和部门名称。
条件：emp incming max ( age)
结果：name dept_name
方法一：
select name,dept_name from dept left join emp on dept.dept1=emp.dept2 where age=(SELECT max(age) from dept left join emp on dept.dept1=emp.dept2 WHERE incoming between 7500 and 8500 )andincoming between 7500 and 8500 ;
方法二：
SELECT name,dept_name from (SELECT * from emp INNER JOIN dept on emp.dept2=dept.dept1 ORDER BY age desc) a where incoming>=7500 and incoming<=8500 LIMIT 1;
方法三：
SELECT name,dept_name FROM (SELECT * FROM dept inne JOIN emp on dept1=dept2 where incoming between 7500 and 8500)b WHERE age=(SELECT max(age) FROM (SELECT * FROM dept inne JOIN emp on dept1=dept2 where incoming between 7500 and 8500)b)
方法四：
SELECT name,dept_name FROM (SELECT * FROM dept inne JOIN emp on dept1=dept2 where incoming between 7500 and 8500)b ORDER BY age desc LIMIT 1
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