数据：
Student(Sid,Sname,Sage,Ssex)学生表
Sid：学号 Sname：学生姓名 Sbirth：学生生日 Ssex：学生性别
01 赵雷 1990-01-01 男
02 钱电 1990-12-21 男
03 孙风 1990-05-20 男
04 李云 1990-08-06 男
05 周梅 1991-12-01 女
06 吴兰 1992-03-01 女
07 郑竹 1989-07-01 女
08 王菊 1990-01-20 女
Course(Cid,Cname,T#)课程表
Cid：课程编号 Cname：课程名称 Tid：教师编号
01 语文 02
02 数学 01
03 英语 03
Teacher(Tid,Tname)教师表
Tid：教师编号 Tname：教师名字
01 张三
02 李四
03 王五
SC(Sid,Cid,score)成绩表
Sid：学号 Cid：课程编号 score：成绩
01 01 80
01 02 90
01 03 99
02 01 70
02 02 60
02 03 80
03 01 80
03 02 80
03 03 80
04 01 50
04 02 30
04 03 20
05 01 76
05 02 87
06 01 31
06 03 34
07 02 89
07 03 98
1 show databases; 2 use work8; 3 show tables;
//1：查询01课程比02课程成绩高的所有学生的学号
4 with 5 a as (select s.sid,score from student s left join sc on s.sid=sc.sid and cid=1), 6 b as (select s.sid,score from student s left join sc on s.sid=sc.sid and cid=2), 7 c as (select a.sid,a.score score1,b.score score2 from a left join b on a.sid=b.sid) 8 select sid from c where score1>score2;
//2：按平均成绩从高到低显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，
//--按如下形式显示：学生ID，数据库，企业管理，英语，有效课程数，有效平均分 9 //--按如下形式显示：学生ID，语文成绩，数学成绩，英语成绩，有效课程数，有效平均分 10 with 11 a as (select s.sid,sc1.score,sc2.score,sc3.score from student s 12 left join sc sc1 on s.sid=sc1.sid and sc1.cid=1 13 left join sc sc2 on s.sid=sc2.sid and sc2.cid=2 14 left join sc sc3 on s.sid=sc3.sid and sc3.cid=3), 15 b as (select sid,count(sc.cid) yx,sum(score) ,round(sum(score)/count(sc.cid),2) av from sc group by sid ) 16 select a.*,b.yx,b.av from a right join b on a.sid=b.sid order by av desc;
// 17 select sid,count(sc.cid) yx,sum(score) ,round(sum(score)/count(sc.cid),2) av from sc group by sid order by av desc; 18 //3：查询各科成绩最高和最低的分：以如下的形式显示：课程ID，最高分，最低分 19 select cid,max(score),min(score) from sc group by cid; 20 //4：查询各科成绩前三名的记录（不考虑成绩并列情况） 21 select b.cname,a.score,a.rk from 22 (select sc.*,row_number() over (distribute by cid sort by score desc ) rk from sc ) a 23 join course b on a.cid=b.cid and a.rk<4; 24 //5：查询男生、女生人数 25 select ssex,count(1) from student group by ssex; 26 //6：求选了课程的学生人数 27 select count(0) from (select distinct sid from sc) a; 28 //7：查询每门课程成绩最好的前两名 29 select b.cname,c.sname,a.score,a.rk from 30 (select sid,cid,score,rank() over(distribute by cid sort by score desc) rk from sc) a 31 left join course b on a.cid=b.cid 32 left join student c on a.sid=c.sid where rk<3; 33 //8：查询平均成绩大于60分的同学的学号和平均成绩 34 select sid,avg(score) av from sc group by sid having av >60; 35 36 37 38 //1：查询和02号的同学学习的课程完全相同的其他同学学号和姓名 39 select b.sid,s.sname from 40 (select sum(cid) a from sc group by sid having sid=2) a, 41 (select sid,sum(cid) b from sc group by sid) b, 42 student s 43 where a.a=b.b and b.sid =s.sid and b.sid!=2; 44 //2：查询如下课程平均成绩和及格率的百分数(用”1行”显示): 语文（01），数学（02），英语（03） 45 select 46 max(case a.cid when 1 then concat(b.cname,a.av,':',a.pr) else 0 end) as yuwen, 47 max(case a.cid when 2 then concat(b.cname,a.av,":",a.pr) else 0 end)as shuxue , 48 max(case a.cid when 3 then concat(b.cname,a.av,":",a.pr) else 0 end)as yingyv 49 from 50 (select cid,round(avg(score),2) av,concat(round(sum(case when score>60 then 1 else 0 end)/count(score)*100,2),"%") pr from sc group by sc.cid )a join course b on a.cid=b.cid; 51 52 //3：统计下列各科成绩，各分数段人数：课程ID，课程名称，[100-85],[85-70],[70-60],[ 小于60] 53 select b.cname,a.* from 54 (select cid,sum(case when score>85 then 1 else 0 end) as 100_85,sum(case when 85>=score and score>70 then 1 else 0 end) 85_70,sum(case when 70>score and score>60 then 1 else 0 end) 70_60 ,sum(case when score<60 then 1 else 0 end) 60_ from sc group by sc.cid) a 55 join course b on a.cid=b.cid; 56 //4：查询每门课程的平均成绩，结果按平均成绩升序排序，平均成绩相同时，按课程号降序排列 57 select sc.cid,b.cname,avg(score) av from sc left join course b on sc.cid=b.cid group by sc.cid,b.cname order by av asc , sc.cid desc; 58 //5：查询选修“张三”老师所授课程的学生中，成绩最高的学生姓名及其成绩 59 60 select s.sname,sc.score from sc left join course b on sc.cid=b.cid left join teacher c on c.tid=b.tid left join student s on sc.sid=s.sid where c.tname="张三" order by score desc limit 1; 61 //6：查询全部学生选修的课程的课程号和课程名 62 63 select sc.cid,b.cname from sc left join course b on b.cid=sc.cid group by sc.cid ,b.cname;