请创建如下表，并创建相关约束
create table class( cid int auto_increment primary Key, caption char(20) ) default charset=utf8; create table teacher( tid int auto_increment primary key, tname char(20) ) default charset=utf8; create table course( cid int auto_increment primary key, cname char(20), tearch_id int, constraint fk_th foreign key (tearch_id) references teacher(tid) ) default charset=utf8; create table student( sid int auto_increment primary key, sname char(20), gender enum("男","女"), class_id int, constraint fk_sc foreign key (class_id) references class(cid) ) default charset=utf8; create table score( sid int auto_increment primary key, student_id int, corse_id int, number float, constraint fk_ss foreign key (student_id) references student (sid), constraint fk_cs foreign key (corse_id) references course(cid) ) default charset=utf8;
二、操作表
1、自行创建测试数据
insert into class(caption) values ("三年二班"),("一年三班"),("三年一班");
insert into teacher(tname) values ("波多"),("苍空"),("饭岛");
insert into course(cname,tearch_id) values ("生物","1"),("体育","1"),("物理","2");
insert into student(sname,gender,class_id) values ("钢蛋","女","1"),("铁锤","女","1"),("山炮","男","2");
insert into student(sname,gender,class_id) values ("钢蛋","女","1"),("铁锤","女","1"),("山炮","男","2");
insert into score(student_id,corse_id,number) values ("1","1","60"),("1","2","59"),("2","2","100");
2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
select a.student_id from
(select score.student_id,score.number,course.cname from score left join course on score.corse_id = course.cid where cname = "生物") as a
left join
(select score.student_id,score.number,course.cname from score left join course on score.corse_id = course.cid where cname = "体育") as b
on a.student_id = b.student_id
where a.number > b.number
;
3、查询平均成绩大于60分的同学的学号和平均成绩；
select student_id,avg(number) from score group by student_id having avg(number) > 60;
4、查询所有同学的学号、姓名、选课数、总成绩；
select score.student_id,student.sname,count(score.corse_id),sum(score.number) from
score left join student on score.student_id = student.sid
group by score.student_id;
5、查询姓“李”的老师的个数；
select count(tid) from teacher where tname like '饭%';
6、查询没学过“叶平”老师课的同学的学号、姓名；
select score.student_id,student.sname from
score left join student on score.student_id = student.sid
where score.corse_id not in
(select course.cid from course left join teacher on course.tearch_id = teacher.tid where teacher.tname = "波多");
7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
select a.student_id from
(select student_id,corse_id from score where corse_id = "1") as a
right join
(select student_id,corse_id from score where corse_id = "2") as b
on a.student_id = b.student_id
where a.student_id = b.student_id
;
8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
select score.student_id,student.sname from
score left join student on score.student_id = student.sid
where score.corse_id in
(select course.cid from course left join teacher on course.tearch_id = teacher.tid where teacher.tname = "波多") group by score.student_id;
9、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；
select c.student_id,student.sname from
(select a.student_id from
(select student_id,number from score where corse_id = "1") as a
right join
(select student_id,number from score where corse_id = "2") as b
on a.student_id = b.student_id
where a.number > b.number) as c
left join student on
c.student_id = student.sid;
10、查询课程成绩小于60分的同学的学号、姓名；
select score.student_id,student.sname from score left join student on score.student_id = student.sid
where score.number < 60;
11、查询没有学全所有课的同学的学号、姓名；
select score.student_id,student.sname from score
left join student on score.student_id = student.sid
group by score.student_id having count(corse_id) <
(select count(cid) from course)
;
12、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名；
select score.student_id,student.sname from score left join student on score.student_id = student.sid
where score.corse_id in
(select corse_id from score where student_id = 1) and score.student_id != 1;
13、查询至少学过学号为“001”同学所选课程中任意一门课的其他同学学号和姓名；
14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名；
select a.student_id,a.sname from
(select score.student_id,student.sname,score.corse_id from score left join student on score.student_id = student.sid)as a
left join
(select score.student_id,score.corse_id from score where student_id = 2)as b
on a.student_id = b.student_id
where a.corse_id = b.corse_id and a.student_id !=2
;
15、删除学习“叶平”老师课的SC表记录；
delete from score where corse_id in
(select course.cid from course left join teacher on course.tearch_id = teacher.tid
where teacher.tname = "苍空");
16、向SC表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“002”课程的同学学号；②插入“002”号课程的平均成绩；
insert into score(student_id,corse_id,number)
select student_id,corse_id,(select avg(number) from score where student_id = 2) as avg_number from score where corse_id not in
(select corse_id from score where student_id = 2);
17、按平均成绩从低到高显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
select sc.student_id,
(select num from score left join course on score.course_id = course.cid where course.cname = "生物" and score.student_id=sc.student_id) as sy,
(select num from score left join course on score.course_id = course.cid where course.cname = "物理" and score.student_id=sc.student_id) as wl,
(select num from score left join course on score.course_id = course.cid where course.cname = "体育" and score.student_id=sc.student_id) as ty,
count(sc.course_id),
avg(sc.num)
from score as sc
group by student_id desc
18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分；
select corse_id,max(number),mix(number) from score group by corse_id;
19、按各科平均成绩从低到高和及格率的百分数从高到低顺序；
select course_id, avg(num) as avgnum,sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent from score group by course_id order by avgnum asc,percent desc;
20、课程平均分从高到低显示（现实任课老师）；
select avg(if(isnull(score.num),0,score.num)),teacher.tname from course
left join score on course.cid = score.course_id
left join teacher on course.teacher_id = teacher.tid
group by score.course_id
21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
(
select
sid,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 3,1) as second_num
from
score as s1
) as T
on score.sid =T.sid
where score.num <= T.first_num and score.num >= T.second_num
22、查询每门课程被选修的学生数；
select course_id, count(1) from score group by course_id;
23、查询出只选修了一门课程的全部学生的学号和姓名；
select student.sid, student.sname, count(1) from score
left join student on score.student_id = student.sid
group by course_id having count(1) = 1
24、查询男生、女生的人数；
select * from
(select count(1) as man from student where gender='男') as A ,
(select count(1) as feman from student where gender='女') as B
25、查询姓“张”的学生名单；
select sname from student where sname like '张%';
26、查询同名同姓学生名单，并统计同名人数；
select sname,count(1) as count from student group by sname;
27、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；
select course_id,avg(if(isnull(num), 0 ,num)) as avg from score group by course_id order by avg asc,course_id desc;
28、查询平均成绩大于85的所有学生的学号、姓名和平均成绩；
select student_id,sname, avg(if(isnull(num), 0 ,num)) from score left join student on score.student_id = student.sid group by student_id;
29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
select student.sname,score.num from score
left join course on score.course_id = course.cid
left join student on score.student_id = student.sid
where score.num < 60 and course.cname = '生物'
30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
select * from score where score.student_id = 3 and score.num > 80
31、求选了课程的学生人数
select count(distinct student_id) from score
select count(c) from (
select count(student_id) as c from score group by student_id) as A
32、查询选修“杨艳”老师所授课程的学生中，成绩最高的学生姓名及其成绩；
select sname,num from score
left join student on score.student_id = student.sid
where score.course_id in (select course.cid from course left join teacher on course.teacher_id = teacher.tid where tname='张磊老师') order by num desc limit 1;
33、查询各个课程及相应的选修人数；
select course.cname,count(1) from score
left join course on score.course_id = course.cid
group by course_id;
34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；
select DISTINCT s1.course_id,s2.course_id,s1.num,s2.num from score as s1, score as s2 where s1.num = s2.num and s1.course_id != s2.course_id;
35、查询每门课程成绩最好的前两名；
select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
(
select
sid,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
(select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num
from
score as s1
) as T
on score.sid =T.sid
where score.num <= T.first_num and score.num >= T.second_num
36、检索至少选修两门课程的学生学号；
select student_id from score group by student_id having count(student_id) > 1;
37、查询全部学生都选修的课程的课程号和课程名；
elect course_id,count(1) from score group by course_id having count(1) = (select count(1) from student);
38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；
select student_id,student.sname from score
left join student on score.student_id = student.sid
where score.course_id not in (
select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '张磊老师'
)
group by student_id
39、查询两门以上不及格课程的同学的学号及其平均成绩；
select student_id,count(1) from score where num < 60 group by student_id having count(1) > 2
40、检索“004”课程分数小于60，按分数降序排列的同学学号；
select student_id from score where num< 60 and course_id = 4 order by num desc;
41、删除“002”同学的“001”课程的成绩；
delete from score where course_id = 1 and student_id = 2