sql练习
-- 学生表
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
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
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
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);
-- 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 * from student s right JOIN
(select t1.SId, class1, class2 from
(select SId, score as class1 from sc where CId = '01') as t1,
(select SId, score as class2 from sc where CId = '02') as t2
where t1.SId = t2.SId and t1.class1>t2.class2) t
on s.SId=t.SId */
-- 1.1 查询同时存在" 01 "课程和" 02 "课程的情况
/* select t1.SId, class1, class2 from
(select SId, score as class1 from sc where CId = '01') as t1,
(select SId, score as class2 from sc where CId = '02') as t2
where t1.SId = t2.SId */
-- 1.2 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 t1.SId, class1, class2 from
(select SId, score as class1 from sc where CId = '01') as t1 left JOIN
(select SId, score as class2 from sc where CId = '02') as t2
on t1.SId = t2.SId */
-- 1.3 查询不存在" 01 "课程但存在" 02 "课程的情况
/* select * from sc
where sc.SId not in (
select SId from sc
where sc.CId = '01'
)
AND sc.CId= '02'; */
-- 2. 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 s.SId,Sname,t.avgscore from student s INNER JOIN
(select SId,avg(score) as avgscore from sc GROUP BY SId HAVING AVG(score)>= 60) t
on s.SId=t.SId */
-- 3. 查询在 SC 表存在成绩的学生信息
/* select distinct s.* from student s , sc t
where s.SId=t.SId */
-- 4. 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 s.SId, Sname, counts, sums from student s LEFT JOIN
(select SId, count(score) as counts, sum(score) as sums from sc GROUP BY SId) t
on s.SId=t.SId */
-- 4.1 查有成绩的学生信息
/* select * from student s where exists(SELECT 1 from sc where s.SId=sc.SId) */
-- 5. 查询「李」姓老师的数量
/* select count(TId) from teacher where Tname LIKE '李%' */
-- 6. 查询学过「张三」老师授课的同学的信息
/* select student.* from student,teacher,course,sc
where
student.sid = sc.sid
and course.cid=sc.cid
and course.tid = teacher.tid
and tname = '张三'; */
-- 7. 查询没有学全所有课程的同学的信息
/* SELECT s.* from student s where s.SId not in
(select SId from sc GROUP BY SId
HAVING count(CId)=(select count(CId) from course)) */
-- 8. 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 s.* from student s,
(select DISTINCT SId from sc where CId in (select CId from sc where SId = '01') and SId != '01') t
where s.SId=t.SId */
-- 9. 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 s.* from student s,
(select SId from sc GROUP BY SId having GROUP_CONCAT(CId ORDER BY CId)=(select GROUP_CONCAT(CId ORDER BY CId) from sc where SId = '01' ) and SId != '01') t
where s.SId=t.SId */
-- 10. 查询没学过"张三"老师讲授的任一门课程的学生姓名
/* select * from student
where SId not in
(select SId from sc
where CId in
(select CId from course,teacher
where course.TId=teacher.TId and Tname='张三')) */
-- 11. 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 t.SId,Sname,avgs from student,(
select SId,avg(score) as avgs from sc where score<60 GROUP BY SId having count(CId)>=2) t
where student.SId=t.SId */
-- 12. 检索" 01 "课程分数小于 60，按分数降序排列的学生信息
select student.* from student,(
select SId from sc where CId='01' and score<60 ORDER BY score DESC) t
where student.SId=t.SId
-- 13. 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 * from sc
left join (
select sid,avg(score) as avscore from sc
group by sid
)r
on sc.sid = r.sid
order by avscore desc; */
-- 14. 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 sc.CId,count(SId) as counts,Cname,max(score),min(score),avg(score),
sum(case when score >= 60 then 1 else 0 end)/count(SId) '及格率',
sum(case when score >= 70 and score <= 80 then 1 else 0 end)/count(SId) '中等率',
sum(case when score >= 80 and score <= 90 then 1 else 0 end)/count(SId) '优良率',
sum(case when score >= 90 then 1 else 0 end)/count(SId) '优秀率'
from sc
RIGHT JOIN course c on c.CId=sc.CId
group by sc.CId order by counts desc, sc.CId asc */
-- 15. 按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺
/* select a.CId,a.SId,a.score,count(b.score)+1 as rank from sc a left JOIN sc b
on a.CId = b.CId and a.score<b.score
GROUP BY a.CId, a.SId
ORDER BY a.CId, rank asc */
-- 15.1 按各科成绩进行排序，并显示排名， Score 重复时合并名次
/* 有问题
select a.CId,GROUP_CONCAT(DISTINCT a.SId ),a.score,count(b.score)+1 as rank from sc a left JOIN sc b
on a.CId = b.CId and a.score<b.score
GROUP BY a.CId,a.score
ORDER BY a.CId, a.score desc */
-- 16. 查询学生的总成绩，并进行排名，总分重复时保留名次空缺【不会】
-- 16.1 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
/* set @crank=0;
select q.sid, total, @crank := @crank +1 as rank from(
select sc.sid, sum(sc.score) as total from sc
group by sc.sid
order by total desc)q; */
-- 17. 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 sc.CId, Cname,
sum(case when score < 60 then 1 else 0 end) '[60-0]',
sum(case when score < 60 then 1 else 0 end)/count(score) '[60-0]%',
sum(case when score >=60 and score < 70 then 1 else 0 end) '[70-60]',
sum(case when score >=60 and score < 70 then 1 else 0 end)/count(score) '[70-60]%',
sum(case when score >=70 and score < 85 then 1 else 0 end) '[85-70]',
sum(case when score >=70 and score < 85 then 1 else 0 end)/count(score) '[85-70]%',
sum(case when score >=85 and score <= 100 then 1 else 0 end) '[100-85]',
sum(case when score >=85 and score <= 100 then 1 else 0 end)/count(score) '[100-85]%'
from sc,course
where sc.CId=course.CId
GROUP BY sc.CId */
-- 18. 查询各科成绩前三名的记录
/* 有问题
select a.CId,a.SId, a.score score1 from sc a
left join sc b
on a.CId=b.CId and a.score < b.score
GROUP BY a.CId, a.SId
having count(b.score) < 3
ORDER BY a.CId, score1 desc */
-- 19. 查询每门课程被选修的学生数
/* select CId, count(SId) '学生数' from sc group by CId */
-- 20. 查询出只选修两门课程的学生学号和姓名
/* select s.SId, Sname from student s right JOIN (
select SId from sc group by SId having count(CId) = 2) t
on s.SId=t.SId */
-- 21. 查询男生、女生人数
/* select ssex, count(*) from student
group by ssex; */
-- 22. 查询名字中含有「风」字的学生信息
/* select *
from student
where student.Sname like '%风%' */
-- 23. 查询同名同性学生名单，并统计同名人数
/* select sname, count(*),ssex from student
group by sname,Ssex
having count(*)>1; */
-- 24. 查询 1990 年出生的学生名单
/* select *
from student
where YEAR(student.Sage)=1990; */
-- 25. 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, course.cname, AVG(SC.SCORE) as average from sc, course
where sc.cid = course.cid
group by sc.cid
order by average desc,cid asc; */
-- 26. 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 student.sid, student.sname, AVG(sc.score) as aver from student, sc
where student.sid = sc.sid
group by sc.sid
having aver > 85; */
-- 27. 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, sc.score from student, sc, course
where student.sid = sc.sid
and course.cid = sc.cid
and course.cname = "数学"
and sc.score < 60; */
-- 28. 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 student.sname, cid, score from student
left join sc
on student.sid = sc.sid; */
-- 29. 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 s.sid,c.cname,t.score from student s, (
select distinct SId,CId,score from sc where score >= 70) t, course c
where s.SId = t.SId and c.CId=t.cid */
-- 30. 查询不及格的课程
/* select DISTINCT sc.CId
from sc
where sc.score <60; */
-- 31. 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 student.sid,student.sname
from student,sc
where cid="01"
and score>=80
and student.sid = sc.sid; */
-- 32. 求每门课程的学生人数
/* select sc.CId,count(*) as 学生人数
from sc
GROUP BY sc.CId; */
-- 33. 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 student.*, sc.score, sc.cid from student, teacher, course,sc
where teacher.tid = course.tid
and sc.sid = student.sid
and sc.cid = course.cid
and teacher.tname = "张三"
order by score desc
limit 1; */
-- 34. 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
/* UPDATE sc SET score=90
where sid = "07"
and cid ="02";
select student.*, sc.score, sc.cid from student, teacher, course,sc
where teacher.tid = course.tid
and sc.sid = student.sid
and sc.cid = course.cid
and teacher.tname = "张三"
and sc.score = (
select Max(sc.score)
from sc,student, teacher, course
where teacher.tid = course.tid
and sc.sid = student.sid
and sc.cid = course.cid
and teacher.tname = "张三"
); */
-- 35. 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 a.cid, a.sid, a.score from sc as a
inner join
sc as b
on a.sid = b.sid
and a.cid != b.cid
and a.score = b.score
group by cid */
-- 36. 查询每门课程成绩最好的前两名
/* select a.sid,a.cid,a.score from sc as a
left join sc as b
on a.cid = b.cid and a.score<b.score
group by a.cid, a.sid
having count(b.cid)<2
order by a.cid; */
-- 37. 统计每门课程的学生选修人数（超过 5 人的课程才统计）。
/* select sc.cid, count(sid) as cc from sc
group by cid
having cc >5; */
-- 38. 检索至少选修两门课程的学生学号
/* select sid, count(cid) as cc from sc
group by sid
having cc>=2; */
-- 39. 查询选修了全部课程的学生信息
/* select student.*
from sc ,student
where sc.SId=student.SId
GROUP BY sc.SId
HAVING count(*) = (select DISTINCT count(*) from course ) */
-- 40. 查询各学生的年龄，只按年份来算【看第41题】
-- 41. 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 student.SId as 学生编号,student.Sname as 学生姓名,
TIMESTAMPDIFF(YEAR,student.Sage,CURDATE()) as 学生年龄
from student */
-- 42. 查询本周过生日的学生
/* select *
from student
where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE()); */
-- 43. 查询下周过生日的学生
/* select *
from student
where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE())+1; */
-- 44. 查询本月过生日的学生
/* select *
from student
where MONTH(student.Sage)=MONTH(CURDATE()); */
-- 45. 查询下月过生日的学生
/* select *
from student
where MONTH(student.Sage)=MONTH(CURDATE())+1; */