SQL语句练习以及答案 (1)

1.准备工作：

部门表dept（部门序号，部门名，部门位置）
员工表emp（员工编号，名字，职业，直接上级编号，受雇日期，月薪，补贴，部门序号）

--创建使用数据库：
create database scott;
use scott；

--创建表格：
CREATE TABLE DEPT
(DEPTNO INT,
DNAME VARCHAR(20),
LOC VARCHAR(20),
CONSTRAINT PK_DEPT PRIMARY KEY(DEPTNO));

CREATE TABLE EMP
(EMPNO int,
ENAME VARCHAR(20),
JOB VARCHAR(20),
MGR int,
HIREDATE DATE,
SAL int,
COMM int,
DEPTNO int,
CONSTRAINT PK_EMP PRIMARY KEY(EMPNO),
CONSTRAINT FK_DEPTNO FOREIGN KEY (DEPTNO)
REFERENCES DEPT (DEPTNO));

--插入数据
Insert into DEPT (DEPTNO,DNAME,LOC) values (10,'ACCOUNTING','NEW YORK');
Insert into DEPT (DEPTNO,DNAME,LOC) values (20,'RESEARCH','DALLAS');
Insert into DEPT (DEPTNO,DNAME,LOC) values (30,'SALES','CHICAGO');
Insert into DEPT (DEPTNO,DNAME,LOC) values (40,'OPERATIONS','BOSTON');

INSERT INTO `emp` VALUES (7369, 'SMITH', 'CLERK', 7902, '1980-12-17', 800, NULL, 20);
INSERT INTO `emp` VALUES (7499, 'ALLEN', 'SALESMAN', 7698, '1981-2-20', 1600, 300, 30);
INSERT INTO `emp` VALUES (7521, 'WARD', 'SALESMAN', 7698, '1981-2-22', 1250, 500, 30);
INSERT INTO `emp` VALUES (7566, 'JONES', 'MANAGER', 7839, '1981-4-2', 2975, NULL, 20);
INSERT INTO `emp` VALUES (7654, 'MARTIN', 'SALESMAN', 7698, '1981-9-28', 1250, 1400, 30);
INSERT INTO `emp` VALUES (7698, 'BLAKE', 'MANAGER', 7839, '1981-5-1', 2850, NULL, 30);
INSERT INTO `emp` VALUES (7782, 'CLARK', 'MANAGER', 7839, '1981-6-9', 2450, NULL, 10);
INSERT INTO `emp` VALUES (7788, 'SCOTT', 'ANALYST', 7566, '1987-4-19', 3000, NULL, 20);
INSERT INTO `emp` VALUES (7839, 'KING', 'PRESIDENT', NULL, '1981-11-17', 5000, NULL, 10);
INSERT INTO `emp` VALUES (7844, 'TURNER', 'SALESMAN', 7698, '1981-9-8', 1500, 0, 30);
INSERT INTO `emp` VALUES (7876, 'ADAMS', 'CLERK', 7788, '1987-5-23', 1100, NULL, 20);
INSERT INTO `emp` VALUES (7900, 'JAMES', 'CLERK', 7698, '1981-12-3', 950, NULL, 30);
INSERT INTO `emp` VALUES (7902, 'FORD', 'ANALYST', 7566, '1981-12-3', 3000, NULL, 20);
INSERT INTO `emp` VALUES (7934, 'MILLER', 'CLERK', 7782, '1982-1-23', 1300, NULL, 10);

2.练习题以及答案：

--1.查询至少有一个员工的部门
SELECT *FROM dept
WHERE deptno IN (SELECT DEPTNO FROM emp);

SELECT *FROM dept
WHERE EXISTS (SELECT * FROM emp WHERE dept.deptno = emp.deptno)

--2.查询薪水比S
c43a
MITH高的员工信息

SELECT * FROM emp
WHERE sal >(SELECT sal FROM emp WHERE ename = 'SMITH')

--3.查询最低薪水低于1500的所有工作和最低薪水
SELECT job,MIN(sal) FROM emp
WHERE MIN(sal) < 1500
*WHERE 字句中不能有聚合函数,应修改为如下：
SELECT job,MIN(sal) FROM emp
WHERE sal < 1500
GROUP BY job
*HAVING 字句中可以使用聚合函数,如下：
SELECT job,MIN(sal)
FROM emp
GROUP BY job
HAVING MIN(sal)<1500

--4.查询部门编号为10号的员工信息
SELECT *
FROM emp
WHERE deptno = 10

--5.查询工资在2000到3000之间的员工所有信息
SELECT *
FROM emp
WHERE sal BETWEEN 2000 AND 3000

--6.查询有补贴的员工信息
SELECT *
FROM emp
WHERE comm IS NOT NULL

--7.查询是否有员工叫SMITH,KING,OBAMA的？
SELECT *
FROM emp
WHERE ename IN ('SMITH','king','OBAMA')
*注意以上king小写也能查出，若要区分大小写，修改如下：
SELECT *
FROM emp
WHERE ename COLLATE utf8_bin
IN ('SMITH','king','OBAMA')

--8.查询S开头的员工信息
SELECT *
FROM emp
WHERE ename LIKE 'S%'

--9.查询第二个字母是A的员工信息
SELECT *
FROM emp
WHERE ename LIKE '_A%'

--10.查询1982年之后入职的员工信息
SELECT *
FROM emp
WHERE hiredate > '1982'

11.查询各部门的平均薪资
SELECT AVG(sal)
FROM emp
GROUP BY deptno

+查询各部门的部门名和平均薪资

SELECT dname,AVG(sal)
FROM dept LEFT JOIN emp ON dept.deptno = emp.deptno
GROUP BY dept.deptno

12.查询各部门各岗位的平均薪资和最高薪资
SELECT deptno,job,AVG(sal),MAX(sal)
FROM emp
GROUP BY deptno ,job

查询各部门各岗位的部门名，岗位名，平均薪资和最高薪资

SELECT dname,job,AVG(sal),MAX(sal)
FROM dept LEFT JOIN emp ON dept.deptno = emp.deptno
GROUP BY dname,job

13.查询各个部门经理的最低薪水
SELECT  deptno, MIN(sal)
FROM emp
WHERE job ='MANAGER'
GROUP BY deptno

14.查询所有员工的年薪，并按照年薪从高到低排序
SELECT empno,sal*12+IFNULL (comm,0) AS 年薪
FROM emp
ORDER BY 年薪 DESC

15.查询比30部门最高薪资的人薪资更高的所有员工信息
SELECT *
FROM emp
WHERE sal >
(SELECT MAX(sal) FROM emp WHERE deptno = '30')

查询比30部门所有人薪资都高员工信息
SELECT *
FROM emp
WHERE sal >
ALL (SELECT sal FROM emp WHERE deptno = '30')

16.查询每一个员工的姓名，职位以及领导的姓名
SELECT a.ename,a.job,b.ename AS 领导
FROM emp a LEFT JOIN emp b ON a.mgr = b.empno

SELECT a.ename,a.job,b.ename AS 领导
FROM emp a,emp b
WHERE a.mgr = b.empno

17.查询部门号为10号的部门名，员工名。以及薪资
SELECT dname,ename,sal
FROM emp,dept
WHERE emp.deptno = dept.deptno
AND emp.deptno = '10'

18.查询在销售部工作的员工姓名
SELECT ename
FROM emp
WHERE deptno =
(SELECT deptno FROM dept WHERE dname = 'SALES')

19.查询ford的详细信息，以及领导姓名
SELECT a.* ,b.ename 领导
FROM emp a,emp b
WHERE a.mgr = b.empno
AND a.ename = 'ford'

20.查询薪水高于公司的平均水平的所有员工名字以及薪水
SELECT ename ,sal
FROM emp
WHERE sal >
(SELECT AVG(sal) FROM emp )

1. 查询各个部门中工资最高的员工信息：名字、部门号、工资
SELECT ename,deptno,sal
FROM emp
WHERE (sal,deptno) IN
(SELECT MAX(sal),deptno FROM emp GROUP BY deptno)

2. 查询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，并根据部门号排序
SELECT b.deptno,b.dname,a.*
FROM dept b LEFT JOIN emp a ON a.deptno = b.deptno
ORDER BY b.deptno ASC

3. 查询各个管理者属下员工的最低工资，其中最低工资不能低于800，没有管理者的员工不计在内
SELECT mgr 管理者,ename 员工,MIN(sal)
FROM emp
WHERE sal >= 800
AND mgr IS NOT NULL
GROUP BY mgr

4. 哪个部门的平均工资是最高的，列出部门号和平均工资
SELECT deptno ,AVG(sal) 平均
FROM emp
GROUP BY deptno
ORDER BY 平均 DESC LIMIT 0,1

思路：
1.求出所有部门的平均工资
2.从所有的平均工资找到最高的平均工资
3.百所有部门的平均工资和找出最高工资比较，相等的话取出部门ID和平均工资

SELECT b.deptno,b.sal
FROM (SELECT deptno,AVG(sal) AS sal FROM emp GROUP BY deptno) AS b
WHERE b.sal = (SELECT MAX(sal) FROM (SELECT AVG( sal) AS sal FROM emp GROUP BY deptno) AS a)