一、数据准备

1、数据表介绍

--1.学生表 Student(SId,Sname,Sage,Ssex) --SId 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别 --2.课程表 Course(CId,Cname,TId) --CId 课程编号,Cname 课程名称,TId 教师编号 --3.教师表 Teacher(TId,Tname) --TId 教师编号,Tname 教师姓名 --4.成绩表 SC(SId,CId,score) --SId 学生编号,CId 课程编号,score 分数 

2、数据引入

-- 学生表 Student create table Student(SId varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10)); insert into Student values('01' , '赵雷' , '1990-01-01' , '男'); insert into Student values('02' , '钱电' , '1990-12-21' , '男'); insert into Student values('03' , '孙风' , '1990-12-20' , '男'); insert into Student values('04' , '李云' , '1990-12-06' , '男'); insert into Student values('05' , '周梅' , '1991-12-01' , '女'); insert into Student values('06' , '吴兰' , '1992-01-01' , '女'); insert into Student values('07' , '郑竹' , '1989-01-01' , '女'); insert into Student values('09' , '张三' , '2017-12-20' , '女'); insert into Student values('10' , '李四' , '2017-12-25' , '女'); insert into Student values('11' , '李四' , '2012-06-06' , '女'); insert into Student values('12' , '赵六' , '2013-06-13' , '女'); insert into Student values('13' , '孙七' , '2014-06-01' , '女'); -- 科目表 Course create table Course(CId varchar(10),Cname nvarchar(10),TId varchar(10)); insert into Course values('01' , '语文' , '02'); insert into Course values('02' , '数学' , '01'); insert into Course values('03' , '英语' , '03'); -- 教师表 Teacher create table Teacher(TId varchar(10),Tname varchar(10)); insert into Teacher values('01' , '张三'); insert into Teacher values('02' , '李四'); insert into Teacher values('03' , '王五'); -- 成绩表 SC create table SC(SId varchar(10),CId varchar(10),score decimal(18,1)); insert into SC values('01' , '01' , 80); insert into SC values('01' , '02' , 90); insert into SC values('01' , '03' , 99); insert into SC values('02' , '01' , 70); insert into SC values('02' , '02' , 60); insert into SC values('02' , '03' , 80); insert into SC values('03' , '01' , 80); insert into SC values('03' , '02' , 80); insert into SC values('03' , '03' , 80); insert into SC values('04' , '01' , 50); insert into SC values('04' , '02' , 30); insert into SC values('04' , '03' , 20); insert into SC values('05' , '01' , 76); insert into SC values('05' , '02' , 87); insert into SC values('06' , '01' , 31); insert into SC values('06' , '03' , 34); insert into SC values('07' , '02' , 89); insert into SC values('07' , '03' , 98); 

二、问题与答案

1.查询” 01 “课程比” 02 “课程成绩高的学生的信息及课程分数

select  Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别,  SCtmp.c1sc "课程01成绩", SCtmp.c2sc "课程02成绩" from Student natural join (select   c1.SId, c1.score c1sc,   c2.score c2sc  from SC c1  left join SC c2  on    c1.Sid = c2.Sid  where    c1.score > c2.score   and c1.Cid = '01' and c2.Cid = '02') SCtmp; 

2.查询同时存在” 01 “课程和” 02 “课程的情况

select  Student.SId 学号, Sname 姓名, Ssex 性别,  SCtmp.c1sc "课程01成绩", SCtmp.c2sc "课程02成绩" from Student natural join (select   c1.SId, c1.score c1sc,   c2.score c2sc  from SC c1  left join SC c2  on    c1.Sid = c2.Sid  where    c1.Cid = '01' and c2.Cid = '02') SCtmp; 

3.查询存在” 01 “课程但可能不存在” 02 “课程的情况(不存在时显示为 null)

select c1.SId 学号, c1sc "课程01成绩", c2sc "课程02成绩" from (select SId, score c1sc from SC where CId = '01') c1  left join (select SId, score c2sc from SC where CId = '02') c2  on c1.SId = c2.SId; 

4.查询不存在” 01 “课程但存在” 02 “课程的情况

select c2.SId 学号, c1sc "课程01成绩", c2sc "课程02成绩" from (select SId, score c1sc from SC where CId = '01') c1  right join (select SId, score c2sc from SC where CId = '02') c2  on c1.SId = c2.SId; 

5.查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩

select SC.SId 学生编号, Sname 学生姓名, avg(score) 平均成绩 from SC natural join Student group by SC.SId having avg(score) >= 60; 

6.查询在 SC 表存在成绩的学生信息

select Student.SId 学生编号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student natural join (select SId from SC group by SId) tmp; 

7.查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null)

select Student.SId 学生编号, Sname 学生姓名, count(score) 选课总数, sum(score) 总成绩 from SC right join Student on Student.SId = SC.SId group by Student.SId; 

8.查询「李」姓老师的数量

select count(*) 李姓老师数量 from teacher where Tname like concat('李','%'); 

9.查询学过「张三」老师授课的同学的信息

select  Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student natural join SC where SC.CId = (select CId from course natural join teacher where Tname = '张三'); 

10.查询没有学全所有课程的同学的信息

select  Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student where  Student.SId not in (select SId   from SC   group by SId   having count(*) = (select count(*) from course)); 

11.查询至少有一门课与学号为” 01 “的同学所学相同的同学的信息

select distinct Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student natural join SC where CId in (select CId from SC where SId = '01'); 

12.查询和” 01 “号的同学学习的课程 完全相同的其他同学的信息

select   Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student natural join SC sc1 join (select SId, CId from SC where SId = '01') sc2 on sc1.CId = sc2.CId group by sc1.SId having count(*) = (select count(*) from SC sc3 where sc3.SId = sc1.SId) -- 连接查询后选课数等于原来选课数的 and count(*) = (select count(*) from SC where SId = '01'); -- 并且选课数等于要选课相同的人的选课数 

13.查询没学过”张三”老师讲授的任一门课程的学生姓名

select Sname 姓名 from Student where Sid not in (select distinct Sid  from SC  natural join course  natural join teacher  where tname = '张三'); 

14.查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

select   Student.SId 学号, Sname 姓名, avg(score) 平均成绩 from Student natural join SC where SId in (select SId  from SC  where score < 60 group by SId  having count(*) >= 2) group by SId; 

15.检索” 01 “课程分数小于 60，按分数降序排列的学生信息

select  Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别,  score "课程01分数" from Student natural join SC where  CId = '01' and score < 60 order by score desc; 

16.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

select stu.SId 学生编号, Sname 学生姓名, avg(sc4.score) 平均成绩 from Student stu left join SC sc1 on  stu.SId = sc1.SId  and sc1.CId = '01' left join SC sc2 on  stu.SId = sc2.SId  and sc2.CId = '02' left join SC sc3 on  stu.SId = sc3.SId  and sc3.CId = '03' left join SC sc4 on stu.SId = sc4.SId group by stu.SId order by 3 desc; 

17.查询各科成绩最高分、最低分和平均分

以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率 及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90
要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列

select  course.CId 课程号, Cname 课程名, max(score) 最高分, min(score) 最低分, avg(score) 平均分, count(*) 选修人数, sum(if(score >= 60, 1, 0)) / count(*) 及格率, sum(if(score >= 70 and score < 80, 1, 0)) / count(*) 中等率, sum(if(score >= 80 and score < 90, 1, 0)) / count(*) 优良率, sum(if(score >= 90, 1, 0)) / count(*) 优秀率 from course left join SC on course.CId = SC.CId group by course.CId order by 6 desc, 1 asc; 

18.按各科平均成绩进行排序，并显示排名， Score 重复时保留名次空缺

select  CId 课程编号,  avgsc 平均分, if(lastsc = thissc, rowid - (@count:=@count+1), rowid - @count:=0) 排名 from ( select CId, avgsc, @lagfield lastsc,@lagfield:=avgsc thissc, @id:=@id+1 rowid   from (select CId, avg(score) avgsc from SC group by CId order by 2 desc) tmp, (select @lagfield:=0) r, (select @id:=0) rk  ) tmp2, (select @count:=0) cnt; 

19.按各科平均成绩进行排序，并显示排名， Score 重复时不保留名次空缺

select CId 课程编号, avgsc 平均分, @id:=@id+1 排名 from (select CId, avg(score) avgsc from SC group by CId order by 2 desc) tmp1, (select @id:=0) tmp2; 

20.查询学生的总成绩，并进行排名，总分重复时保留名次空缺

select  SId 学生编号,  sumsc 总分, if(lastsc = thissc, rowid - (@count:=@count+1), rowid - @count:=0) 排名 from ( select SId, sumsc, @lagfield lastsc,@lagfield:=sumsc thissc, @id:=@id+1 rowid   from (select SId, sum(score) sumsc from SC group by SId order by 2 desc) tmp, (select @lagfield:=0) r, (select @id:=0) rk  ) tmp2, (select @count:=0) cnt; 

21.查询学生的总成绩，并进行排名，总分重复时不保留名次空缺

select SId 课程编号, sumsc 平均分, @id:=@id+1 排名 from (select SId, sum(score) sumsc from SC group by SId order by 2 desc) tmp1, (select @id:=0) tmp2; 

22.统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0]及所占百分比

select  course.CId 课程编号,  Cname 课程名称, sum(if(score >= 85 and score <= 100, 1, 0)) "[85, 100]人数", sum(if(score >= 85 and score <= 100, 1, 0)) / count(*) "[85, 100]占比", sum(if(score >= 70 and score < 85, 1, 0)) "[70, 85)人数", sum(if(score >= 70 and score < 85, 1, 0)) / count(*) "[70, 85)占比", sum(if(score >= 60 and score < 70, 1, 0)) "[60, 70)人数", sum(if(score >= 60 and score < 70, 1, 0)) / count(*) "[60, 70)占比", sum(if(score >= 0 and score < 60, 1, 0)) "[0, 60)人数", sum(if(score >= 0 and score < 60, 1, 0)) / count(*) "[0, 60)占比" from course left join SC on course.CId = SC.CId group by course.CId; 

23.查询各科成绩前三名的记录

select CId 课程号, score 前三分数 from ( (select CId, score from SC where CId = '01' order by score desc limit 3) union all (select CId, score from SC where CId = '02' order by score desc limit 3) union all (select CId, score from SC where CId = '03' order by score desc limit 3) ) res; 

24.查询每门课程被选修的学生数

select course.CId 课程号, Cname 课程名, count(SId) 选修人数 from course left join SC on course.CId = SC.CId group by course.CId; 

25.查询出只选修两门课程的学生学号和姓名

select SC.SId 学号, Sname 姓名 from SC natural join Student group by SC.SId having count(*) = 2; 

26.查询男生、女生人数

select Ssex 性别, count(*) 学生数 from Student group by Ssex; 

27.查询名字中含有「风」字的学生信息

select SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student where Sname like concat('%', '风', '%'); 

28.查询同名同性学生名单，并统计同名人数

select s1.Sname 姓名, s1.Ssex 性别, count(*) 同名人数 from Student s1 join Student s2 on  s1.SId != s2.SId  and s1.Sname = s2.Sname  and s1.Ssex = s2.Ssex group by s1.Sname, s1.Ssex; 

29.查询 1990 年出生的学生名单

select SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student where Year(Sage) = 1990; 

30.查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

select SC.CId 课程号, Cname 课程名, avg(score) 平均分 from SC natural join course group by SC.CId order by 3 desc, 1 asc; 

31.查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩

select SC.SId 学号, Sname 姓名, avg(score) from SC natural join Student group by SC.SId having avg(score) >= 85 order by 3 desc; 

32.查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

select Sname, score from SC natural join Student natural join course where  Cname = '数学' and score < 60; 

33.查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

select  stu.SId 学号, Sname 姓名,  sc1.score 语文, sc2.score 数学, sc3.score 英语 from Student stu left join SC sc1 on  stu.SId = sc1.SId  and sc1.CId = '01' left join SC sc2 on  stu.SId = sc2.SId  and sc2.CId = '02' left join SC sc3 on  stu.SId = sc3.SId  and sc3.CId = '03' order by 1; 

34.查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数

select SC.SId 学号, Sname 姓名, Cname 课程名, score 分数 from SC natural join Student natural join course where score >= 70; 

35.查询不及格的课程

select SC.SId 学号, Sname 姓名, Cname 课程名, score 分数 from SC natural join Student natural join course where score < 60; 

36.查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名

select SC.SId 学号, Sname 姓名 from SC natural join Student where  CId = '01' and score >= 80; 

37.求每门课程的学生人数

select course.CId 课程号, Cname 课程名, count(SId) 选修人数 from course left join SC on course.CId = SC.CId group by course.CId; 

38.成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

select SC.SId 学号, Sname 姓名, score 成绩 from SC natural join Student natural join Teacher natural join course where Tname = '张三' order by score desc limit 1; 

39.成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

select SC.SId 学号, Sname 姓名, score 成绩 from SC natural join Student natural join Teacher natural join course where  Tname = '张三' and score = ( select max(score) from SC      natural join Teacher      natural join course      where Tname = '张三' group by SC.CId     ); 

40.查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

select distinct sc1.SId 学号, sc1.CId 课程号, sc1.score 学生成绩 from SC sc1 join SC sc2 on  sc1.CId != sc2.CId  and sc1.score = sc2.score; 

41.查询每门课程成绩最好的前两名

select CId 课程号, Sname 前二姓名, score 前二成绩 from Student natural join ( (select SId, CId, score from SC where CId = '01' order by score desc limit 2) union (select SId, CId, score from SC where CId = '02' order by score desc limit 2) union (select SId, CId, score from SC where CId = '03' order by score desc limit 2) ) tmp order by 1 asc, 3 desc; 

42.统计每门课程的学生选修人数（超过 5 人的课程才统计）。

select course.CId 课程号, Cname 课程名, count(SId) 选修人数 from course left join SC on course.CId = SC.CId group by course.CId having count(SId) > 5; 

43.检索至少选修两门课程的学生学号

select SC.SId 学号 from SC natural join Student group by SC.SId having count(*) >= 2; 

44.查询选修了全部课程的学生信息

select  Student.SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student where  Student.SId in (select SId   from SC   group by SId   having count(*) = (select count(*) from course)); 

45.查询各学生的年龄，只按年份来算

select  SId 学号, Sname 姓名, year(now()) - year(Sage) 年龄, Ssex 性别 from Student; 

46.按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

select  SId 学号, Sname 姓名, timestampdiff(YEAR, Sage, now()) 年龄, Ssex 性别 from Student; 

47.查询本周过生日的学生

select SId 学号, Sname 姓名 from Student where (weekofyear(date_format(Sage, concat(year(now()), '-%m-%d'))) = weekofyear(now())); 

48.查询下周过生日的学生

select SId 学号, Sname 姓名 from Student where (weekofyear(date_format(Sage, concat(year(now()), '-%m-%d'))) = weekofyear(date_sub(now(), interval 1 week))); 

49.查询本月过生日的学生

select SId 学号, Sname 姓名 from Student where (month(Sage) = month(now())); 

50.查询下月过生日的学生

select SId 学号, Sname 姓名 from Student where (month(Sage) = month(date_sub(now(), interval 1 month)));