前面学习了MySQL的语句的基本用法，这里就开始做一些MySQL练习，这套题目一共45题，属于比较简单的，初学先试着做这个。
参考链接：https://www.cnblogs.com/SJP666/p/4665605.html 感谢博主
一、先创建几个要用的库表
create database ZuoYe; -- 创建数据库 use ZuoYe; -- 使用数据库 #创建几个库表
create table Student -- 学生表
(
Sno char(3) NOT NULL Primary key , -- 学号 ，设为主键，不允许空值
Sname char(8) NOT NULL, -- 学生姓名
Ssex char(2)NOT NULL, -- 学生性别
Sbirthday datetime, -- 学生出生年月
Class char(5) -- 学生所在班级
); create table Teacher -- 教师表
(
Tno char(3)NOT NULL primary key, -- 教工编号设为主键
Tname char(4)NOT NULL, -- 教工姓名
Tsex char(2)NOT NULL, -- 教工性别
Tbirthday datetime, -- 教工出生年月
Prof char(6), -- 职称
Depart varchar(10)NOT NULL -- 教工所在部门
) create table Course -- 课程表
(
Cno char(5) NOT NULL Primary key , -- 课程号设为主键
Cname varchar(10) NOT NULL, -- 课程名称
Tno char(3) NOT NULL references Teacher(Tno) -- 教工编号设为外键
) create table Score -- 成绩表
(
Sno char(3) NOT NULL references Student(Sno), -- 学号设为外码
Cno char(5) NOT NULL references Course(Cno), -- 课程号设为外码
Degree Decimal(4,1), -- 成绩
primary key(Sno,Cno) -- 学号和课程号设为联合主键
)
二、插入数据
insert into Student values(108,'曾华','男','1977-09-01','');
insert into Student values(105,'匡明','男','1975-10-02','');
insert into Student values(107,'王丽','女','1976-01-23','');
insert into Student values(101,'李军','男','1976-02-20','');
insert into Student values(109,'王芳','女','1975-02-10','');
insert into Student values(103,'陆君','男','1974-06-03',''); insert into Teacher values(804,'李诚','男','1958-12-02','副教授','计算机系');
insert into Teacher values(856,'张旭','男','1969-03-12','讲师','电子工程系');
insert into Teacher values(825,'王萍','女','1972-05-05','助教','计算机系') ;
insert into Teacher values(831,'刘冰','女','1977-08-14','助教','电子工程系'); insert into Course values('3-105','计算机导论',825);
insert into Course values('3-245','操作系统',804);
insert into Course values('6-166','数字电路',856);
insert into Course values('9-888','高等数学',831); insert into Score values(103,'3-245',86);
insert into Score values(105,'3-245',75);
insert into Score values(109,'3-245',68);
insert into Score values(103,'3-105',92);
insert into Score values(105,'3-105',88);
insert into Score values(109,'3-105',76);
insert into Score values(101,'3-105',64);
insert into Score values(107,'3-105',91);
insert into Score values(108,'3-105',78);
insert into Score values(101,'6-166',85);
insert into Score values(107,'6-166',79);
insert into Score values(108,'6-166',81);
这个插入语句写的真是粗糙啊，一条条插入。。。懒得改了
三、查询练习（重点）
select * from student;
select * from teacher;
select * from course;
select * from score;
1~5题：
-- 1、查询Student表中的所有记录的Sname、Ssex和Class列。
select sname,ssex,class from student; -- 2、 查询教师所有的单位即不重复的Depart列
select distinct depart from teacher; -- 3、 查询Student表的所有记录。
select * from student; -- 4、 查询Score表中成绩在60到80之间的所有记录
select * from score where degree between 60 and 80; -- 5、 查询Score表中成绩为85，86或88的记录。
select * from score where degree in (85,86,88);
6~10题：
-- 6、 查询Student表中“95031”班或性别为“女”的同学记录。
select * from student where class = '' or Ssex='女'; -- 7、 以Class降序查询Student表的所有记录。
select * from student order by class desc; -- 8、 以Cno升序、Degree降序查询Score表的所有记录。
select * from score ORDER BY cno asc,degree desc; -- 9、 查询“95031”班的学生人数。
select count(1) from student where class = ''; -- 10、 查询Score表中的最高分的学生学号和课程号。（子查询或者排序）
select sno,cno from score where degree = (select max(degree) from score); -- 10.1查询Score表中除了每门课程最高分的学生学号和课程号。（子查询或者排序）
select sno,cno from score where degree not in (select max(degree) from score group by cno)
11~12题：
-- 11、 查询每门课的平均成绩。
select cno,avg(degree) from score group by cno; -- 12、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。
select cno,avg(degree) from score where cno in
(select cno from score group by cno HAVING count(1) > 5 ) and cno like '3%'; -- 13、查询分数大于70，小于90的Sno列。
select sno from score where degree between 70 and 90; -- 14、查询所有学生的Sname、Cno和Degree列。
select student.sname,score.cno , score.degree from score left join student on student.sno = score.sno; -- 15、查询所有学生的Sno、Cname和Degree列。
select score.sno,course.cname,score.degree from score left join course on course.cno = score.cno; -- 16、查询所有学生的Sname、Cname和Degree列。
select student.sname,course.cname,score.degree from score left join student on student.sno = score.sno left join course on score.cno = course.cno; -- 17、 查询“95033”班学生的平均分。
select avg(degree) from score where sno in (select sno from student where class = 95033)
create table Grade(Low int ,Upp int,Rank char(1)) select *from Grade;
insert into Grade values(90,100,'A');
insert into Grade values(80,89,'B');
insert into Grade values(70,79,'C');
insert into Grade values(60,69,'D');
insert into Grade values(0,59,'E');
第十八题：这题不会做，都没做过
-- 现查询所有同学的Sno、Cno和rank列。
select sno,cno,rank from score,grade where degree between low and upp
-- 19、 查询选修“3-105”课程的,并且成绩高于“109”号同学成绩的所有同学的记录。
select * from score where cno = '3-105' and degree > (select degree from score where sno=109 and cno='3-105')
-- 21、 查询成绩高于学号为“109”、课程号为“3-105”的成绩的所有记录。
select * from score where degree > (select degree from score where sno = 109 and cno = '3-105') -- 22、查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。
select * from student;
select sno,sname,sbirthday from student where year(sbirthday) =(select year(sbirthday) from student where sno = 108) -- 23、查询“张旭“教师任课的学生成绩。
select * from teacher where tname = '张旭';
select * from course ;
select * from score where cno = (select cno from course where tno = (select tno from teacher where tname = '张旭')) -- 24、查询选修某课程的同学人数多于5人的教师姓名。
select cno,count(1) from score group by cno HAVING count(1) > 5;
select tname from teacher where tno = (select tno from course where cno = (select cno from score group by cno HAVING count(1) > 5)) -- 25、查询95033班和95031班全体学生的记录。
select * from student where Class in (95033,95031); -- 26、 查询存在有85分以上成绩的课程Cno.
select distinct cno from score where Degree > 85 -- 27、查询出“计算机系“教师所教课程的成绩表。
select tno from teacher where depart = '计算机系';
select cno from course where tno in (select tno from teacher where depart = '计算机系');
select * from score where cno in (select cno from course where tno in (select tno from teacher where depart = '计算机系')); -- 29、查询选修编号为“3-105“课程且成绩至少高于一个选修编号为“3-245”的同学的Cno、Sno和Degree,并按Degree从高到低次序排序。
select * from score where cno = '3-105' and degree > any(select degree from score where cno = '3-245');
#这个其实跟min（degree）是一样的 -- 30、查询选修编号为“3-105”且成绩高于选修编号为“3-245”课程的同学的Cno、Sno和Degree.
select cno,sno,degree from score where cno = '3-105' and degree > all(select degree from score where cno = '3-245');
#这个其实是个max（degree）一样的
第33题之前也不会做，这种类型的都不太会
-- 31、 查询所有教师和同学的name、sex和birthday.
select sname,ssex,sbirthday from student
union ALL
select tname,tsex,tbirthday from teacher; -- 32、查询所有“女”教师和“女”同学的name、sex和birthday.
select sname,ssex,sbirthday from student where ssex = '女'
union ALL
select tname,tsex,tbirthday from teacher where tsex = '女'; -- 33、 查询成绩比该课程平均成绩低的同学的成绩表。
select * from score s1 where degree < (select avg(degree) from score s2 group by cno having s1.cno = s2.cno)
-- 34、 查询所有任课教师的Tname和Depart
select * from teacher;
select DISTINCT cno from score;
select tno from course where cno in (select DISTINCT cno from score);
select tname,depart from teacher where tno in (select tno from course where cno in (select DISTINCT cno from score)) -- 34、 查询所有任课教师的Tname和Depart
select * from teacher;
select DISTINCT cno from score;
select tno from course where cno in (select DISTINCT cno from score);
select tname,depart from teacher where tno in (select tno from course where cno in (select DISTINCT cno from score)); -- 36、查询至少有2名男生的班号。
select class from student where ssex='男' group by class having count(1) >=2 -- 37、查询Student表中不姓“王”的同学记录。
select * from student where sname not like '王%'; -- 38、查询Student表中每个学生的姓名和年龄。
select sname,year(now()) - year(Sbirthday) from student; -- 39、查询Student表中最大和最小的Sbirthday日期值。
select max(sbirthday),min(sbirthday) from student; -- 40、以班号和年龄从大到小的顺序查询Student表中的全部记录。
select * from student ORDER BY class,year(now())-year(sbirthday);
-- 41、查询“男”教师及其所上的课程。
select tno from teacher where tsex = '男';
select * from course where tno in (select tno from teacher where tsex = '男'); -- 42、查询最高分同学的Sno、Cno和Degree列。
select sno,cno,degree from score where degree = (select max(degree) from score); -- 43、查询和“李军”同性别的所有同学的Sname.
select sname from student where ssex = (select ssex from student where sname = '李军'); -- 44、查询和“李军”同性别并同班的同学Sname.
select sname from student where ssex = (select ssex from student where sname = '李军') and class = (select class from student where sname = '李军') -- 45、查询所有选修“计算机导论”课程的“男”同学的成绩表.
select * from course ;
select s.*,c.cname,s2.ssex from score as s left join course as c on s.cno = c.cno left join student as s2 on s.sno = s2.sno;
select * from (select s.*,c.cname,s2.ssex from score as s left join course as c on s.cno = c.cno left join student as s2 on s.sno = s2.sno) as temp where temp.ssex = '男'
and temp.cname = '计算机导论'