student表
teacher表
course表
score表
对这四个表进行一些练习。
1：查询student表中所有记录。
select *from student;
2：查询student表中name/sex/classid这些列。
select name,sex,classid from student;
3：查询教师中不重复的单位department。
select distinct department from teacher;
distinct 列(一个或多个) 获取不重复的记录
4：查询score表中成绩再60至80之间的记录。
select *from score where degree between 60 and 80;
5：查询score表中成绩为85，86，88的记录。
select *from score where degree in (86,85,88);
6：查询student表中为95031班的或性别为女生的。
select *from student where classid=95031 or sex='女';
7：以classid列降序查询student表的所有记录。
select *from student order by desc classid ;
8：以degree降序courseid升序输出score表中所有记录。
select *from score order by courseid asc, degree desc;
9：查询95031班级的人数。
select count(id) from student where classid=95031;
10：查询score表中成绩最高者的记录。
select *from score where degree=(select max(degree) from score);
或： select id,courseid,degree order by degree desc limit 0,1;
11：查询每门课的平均数。
select courseid,avg(degree) from score group by courseid;
12：查询score表中至少2名学生选修以3开头的课程的平均分数。
select courseid, avg(degree) as average from score group by courseid having count(courseid)>1 and courseid like '3%';
13：查询score中分数大于70小于90的id列。
select *from score where degree between 70 and 90;
14：查询学生的name列和degree列和classid列(多表查询)。
select name,degree,classid from student,score where student.id=score.id
15：查询学生的课程id课程名和degree列(多表查询)。
select coursename,degree from score,course where course.courseid=score.courseid;
16：查询学生的姓名成绩和对应课程名。(三表查询)。
select name,degree,coursename from student,course,score where score.id=student.id and score.courseid=course.courseid;
17：查询95031班学生每门课的平均成绩(子查询)。
select avg(degree) from score where id in(select id from student where classid=95031) group by courseid;
18：查询选修3105课程高于109好同学3105课程成绩的同学记录。
select *from score where courseid=3105 and degree>(select degree from score where id=109 and courseid=3105);
19：查询成绩高于学号109课程号为3105的同学的记录。
select *from score where degree>(select degree from score where id=109 and courseid=3105);
20：查询学号与101和108的同学同年出生的学生的记录。
select name, brithday,classid from student where year(brithday) in (select year(brithday) from student where id=108 or id=101);
21：查询张旭老师教的课程学生的成绩。
select *from score where courseid in (select courseid from course where teacherid=(select id from teacher where name='张旭'));
22：查询选修课多余5人的老师的记录。
select *from teacher where id in (select teacherid from course where courseid in (select courseid from score group by courseid having count(courseid)>5));
23：查询95033和95031班级同学的记录
select *from student where classid in (95033,95031);
24：查询88分以上成绩的课程name。
select coursename from course where courseid in(select courseid from score where degree>88);
25：查询计算机系老师所教课程同学的成绩。
select *from score where courseid in(select courseid from course where teacherid in(select id from teacher where department='计算机系'));
26：查询计算机系与电子工程系不同职称的教师的记录。
select *from teacher where department='计算机系'and professional not in (select professional from teacher where department='电子工程系' )
-> union
-> select *from teacher where department='电子工程系'and professional not in (select professional from teacher where department='计算机系' );
27：查询选修编号为3105的课程成绩至少高于部分选修3245课程学生的成绩的记录。
select *from score where courseid=3105 and degree> any(select degree from score where courseid=3245);
28：查询选修编号为3105的课程成绩高于所有选修3245课程学生的成绩的记录。
select *from score where courseid=3105 and degree> all(select degree from score where courseid=3245);
29：查询所有教师和学生的name ,sex ,brithday。
select name,sex,brithday from student
-> union
-> select name,sex,brithday from teacher;
30：查询女教师和女同学的name sex brithday。
select name,sex,brithday from student where sex='女'
-> union
-> select name,sex,brithday from teacher where sex='女';
31：查询成绩比该课程平均分低的同学的成绩。
select *from score a where degree<(select avg(degree) from score b where a.courseid=b.courseid);
32：查询任课老师的name和department。
select *from teacher where id in(select teacherid from course where courseid in(select courseid from score group by courseid));
33：查询班级中至少有2名男生的班级。
select classid from student where sex='男' group by classid having count(classid)>1;
34：查询班级中不姓王的同学。
select *from student where name not like '王%';
35：查询所有学生的姓名和年龄。
select name,year(now())-year(brithday) as age from student;
36：查询学生中年龄最大和年龄最小的数据。
select max(year(now())-year(brithday)),min(year(now())-year(brithday)) from student;
37：以班号和年龄从大到小顺序查询student表中所有记录。
select *from student order by classid,year(now())-year(brithday);
38：查询男教师所上的课程。
select coursename from course where teacherid in (select id from teacher where sex='男')；
39：查询最高分同学的信息。
select *from score where degree =(select max(degree) from score);
40：查询和季军同性别的所有同学。
select *from student where sex=(select sex from student where name='季军');
41：查询和季军同性别并同班的同学的信息。
select *from student where sex=(select sex from student where name='季军') and classid=(select classid from student where name='季军');
42：查询所有选修计算机导论课程的男同学的成绩。
select *from score where courseid=(select courseid from course where coursename='计算机导论') and id in(select id from student where sex='男' );