MySql经典面试题(含表)_max(case c.c when '03' then b.score else null end)

创建数据库表

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

create table Student(SID varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10));

2.课程表

Course(CID,Cname,TID) --CID --课程编号,Cname 课程名称,TID 教师编号

create table Course(CID varchar(10),Cname nvarchar(10),TID varchar(10));

3.教师表

Teacher(TID,Tname) --TID 教师编号,Tname 教师姓名

create table Teacher(TID varchar(10),Tname nvarchar(10));

4.成绩表

SC(SID,CID,score) --SID 学生编号,CID 课程编号,score 分数

create table SC(SID varchar(10),CID varchar(10),score decimal(18,1));

添加数据

1.学生表

insert into Student values('01' , '张三' , '1990-01-01' , '男');
 
insert into Student values('02' , '李四' , '1990-12-21' , '男');
 
insert into Student values('03' , '王五' , '1990-05-20' , '男');
 
insert into Student values('04' , '赵六' , '1990-08-06' , '男');
 
insert into Student values('05' , '田七' , '1991-12-01' , '女');
 
insert into Student values('06' , '孙八' , '1992-03-01' , '女');
 
insert into Student values('07' , '汾九' , '1989-07-01' , '女');
 
insert into Student values('08' , '郑十' , '1990-01-20' , '女');

2.课程表

insert into Course values('01' , '语文' , '02');
 
insert into Course values('02' , '数学' , '01');
 
insert into Course values('03' , '英语' , '03');

3.教师表

insert into Teacher values('01' , '李零');
 
insert into Teacher values('02' , '刘一');
 
insert into Teacher values('03' , '唐二');

4.成绩表

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);

经典例题

#1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数
###1.1、查询同时存在"01"课程和"02"课程的情况
SELECT a.*,b.score 01的成绩,c.score 02的成绩 from student a 
JOIN sc b on a.SID=b.SID and b.CID='01'
JOIN sc c on a.SID=b.SID and c.CID='02'
 
#1.2、查询同时存在"01"课程和"02"课程的情况和存在"01"课程但可能不存在"02"课程的情况(不存在时显示为null)(以下存在相同内容时不再解释)
SELECT a.*,b.score 01的分数,c.score 02的分数 from student a
LEFT JOIN sc b on a.SID=b.SID and b.CID='01'
LEFT JOIN sc c on a.SID=c.SID and c.CID='02'
where IFNULL(b.score,0)
 
#2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数
#2.1、查询同时存在"01"课程和"02"课程的情况
SELECT a.*,b.score 01分数,c.score 02分数  from student a,sc b,sc c
where a.SID=b.SID and a.SID=c.SID and b.CID='01' and c.CID='02' and b.score<c.score
 
#2.2、查询同时存在"01"课程和"02"课程的情况和不存在"01"课程但存在"02"课程的情况
 
SELECT a.*,b.score 01的分数,c.score 02的分数 from student a
LEFT JOIN sc  b on a.SID=b.SID and b.CID='01' 
LEFT JOIN sc c on a.SID=b.SID and c.CID='02'
where IFNULL(b.score,0)
#3、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 a.sid,a.Sname,cast(avg(b.score) as DECIMAL(18,2)) avg_score 
from student a,sc b
where a.SID=b.SID
GROUP BY a.SID,a.Sname
HAVING cast(avg(b.score) as DECIMAL(18,2)) >60
ORDER BY a.SID
 
#4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩
#4.1、查询在sc表存在成绩的学生信息的SQL语句。
 
select a.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score
 
from Student a , sc b
 
where a.SID = b.SID
 
group by a.SID , a.Sname
 
having cast(avg(b.score) as decimal(18,2)) < 60
 
order by a.SID
 
#4.2、查询在sc表中不存在成绩的学生信息的SQL语句。
 
SELECT a.SID,a.Sname,IFNULL(CAST(AVG(b.score) AS DECIMAL(18,2)),0) avg_score from student a
LEFT JOIN sc b on a.SID=b.SID
GROUP BY a.SID,a.Sname
HAVING IFNULL(CAST(AVG(b.score) AS DECIMAL(18,2)),0)<60
ORDER BY a.SID
 
#5、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
#5.1、查询所有有成绩的SQL。
SELECT a.SID 学生编号,a.Sname 学生姓名,count(b.SID) 选课总数,SUM(b.score) 所有课程的总成绩 from student a,sc b
where a.SID=b.SID
GROUP BY a.SID,a.Sname
ORDER BY a.SID
 
#5.2、查询所有(包括有成绩和无成绩)的SQL。
SELECT a.SID 学生编号,a.Sname 学生姓名,count(b.SID) 选课总数,SUM(b.score) 所有课程的总成绩 
from student a
LEFT JOIN sc b
on a.SID=b.SID
GROUP BY a.SID,a.Sname
ORDER BY a.SID
 
#6、查询"李"姓老师的数量
 
#方法1
 
SELECT count(Tname) from teacher where Tname LIKE '李%'
 
###方法2
 
select count(Tname) 李姓老师的数量 from Teacher where left(Tname,1) = '李'
 
#7、查询学过"李零"老师授课的同学的信息
 
SELECT a.* from student a,teacher t ,course c,sc s
where a.SID=s.SID and s.CID=c.CID and c.TID=t.TID and t.Tname='李零'
 
#8、查询没学过"李零"老师授课的同学的信息
sql1:
select m.* from Student m where SID not in (select distinct SC.SID from SC , Course , Teacher where SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = '李零') order by m.SID
 
sql2:
SELECT * from student s where s.SID not in (SELECT s.SID FROM teacher t,course c,sc s where t.TID=c.TID and s.CID=c.CID and Tname ='李零')
 
 
#9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息
 
#方法1
 
select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID
 
#方法2
 
select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '02' and exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '01') order by Student.SID
 
#方法3
 
select m.* from Student m where SID in
 
(
 
select SID from
 
(
 
select distinct SID from SC where CID = '01'
 
union all
 
select distinct SID from SC where CID = '02'
 
) t group by SID having count(1) = 2
 
)
 
order by m.SID
 
#10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息
 
#方法1
 
select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and not exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID
 
#方法2
 
select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and Student.SID not in (Select SC_2.SID from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID
 
#11、查询没有学全所有课程的同学的信息
 
#11.1、
 
select Student.*
 
from Student , SC
 
where Student.SID = SC.SID
 
group by Student.SID , Student.Sname , Student.Sage , Student.Ssex having count(CID) < (select count(CID) from Course)
 
#11.2
 
select Student.*
 
from Student left join SC
 
on Student.SID = SC.SID
 
group by Student.SID , Student.Sname , Student.Sage , Student.Ssex having count(CID) < (select count(CID) from Course)
 
#12、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.* from Student , SC where Student.SID = SC.SID and SC.CID in (select CID from SC where SID = '01') and Student.SID <> '01'
 
#13、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.* from Student where SID in
 
(select distinct SC.SID from SC where SID <> '01' and SC.CID in (select distinct CID from SC where SID = '01')
 
group by SC.SID having count(1) = (select count(1) from SC where SID='01'))
 
#14、查询没学过"李零"老师讲授的任一门课程的学生姓名
 
select student.* from student where student.SID not in
 
(select distinct sc.SID from sc , course , teacher where sc.CID = course.CID and course.TID = teacher.TID and teacher.tname = '李零')
 
order by student.SID
 
#15、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 , student.sname , cast(avg(score) as decimal(18,2)) avg_score from student , sc
 
where student.SID = SC.SID and student.SID in (select SID from SC where score < 60 group by SID having count(1) >= 2)
 
group by student.SID , student.sname
 
#16、检索"01"课程分数小于60，按分数降序排列的学生信息
 
select student.* , sc.CID , sc.score from student , sc
 
where student.SID = SC.SID and sc.score < 60 and sc.CID = '01'
 
order by sc.score desc
 
#17、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#17.1 SQL 2000 静态
 
select a.SID 学生编号 , a.Sname 学生姓名 ,
 
max(case c.Cname when '语文' then b.score else null end) 语文 ,
 
max(case c.Cname when '数学' then b.score else null end) 数学 ,
 
max(case c.Cname when '英语' then b.score else null end) 英语 ,
 
cast(avg(b.score) as decimal(18,2)) 平均分
 
from Student a
 
left join SC b on a.SID = b.SID
 
left join Course c on b.CID = c.CID
 
group by a.SID , a.Sname
 
order by 平均分 desc
 
#17.2 SQL 2000 动态
 
declare @sql nvarchar(4000)
 
set @sql = 'select a.SID ' + '学生编号' + ' , a.Sname ' + '学生姓名'
 
select @sql = @sql + ',max(case c.Cname when '''+Cname+''' then b.score else null end) '+Cname+' '
 
from (select distinct Cname from Course) as t
 
set @sql = @sql + ' , cast(avg(b.score) as decimal(18,2)) ' + '平均分' + ' from Student a left join SC b on a.SID = b.SID left join Course c on b.CID = c.CID
group by a.SID , a.Sname order by ' + '平均分' + ' desc'
 
exec(@sql)
 
#18、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
 
#方法1
 
select m.CID 课程编号 , m.Cname 课程名称 ,
 
max(n.score) 最高分 ,
 
min(n.score) 最低分 ,
 
cast(avg(n.score) as decimal(18,2)) 平均分 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 及格率 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 80 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 中等率 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 80 and score < 90 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优良率 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优秀率
 
from Course m , SC n
 
where m.CID = n.CID
 
group by m.CID , m.Cname
 
order by m.CID
 
#方法2
 
select m.CID 课程编号 , m.Cname 课程名称 ,
 
(select max(score) from SC where CID = m.CID) 最高分 ,
 
(select min(score) from SC where CID = m.CID) 最低分 ,
 
(select cast(avg(score) as decimal(18,2)) from SC where CID = m.CID) 平均分 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 及格率,
 
cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 80 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 中等率 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 80 and score < 90 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优良率 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优秀率
 
from Course m
 
order by m.CID
 
#19、按各科成绩进行排序，并显示排名#19.1 sql 2000用子查询完成
 
#Score重复时保留名次空缺
 
select t.* , px = (select count(1) from SC where CID = t.CID and score > t.score) + 1 from sc t order by t.cid , px
 
#Score重复时合并名次
 
select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t order by t.cid , px
 
#19.2 sql 2005用rank,DENSE_RANK完成
 
#Score重复时保留名次空缺(rank完成)
 
select t.* , px = rank() over(partition by cid order by score desc) from sc t order by t.CID , px
 
#Score重复时合并名次(DENSE_RANK完成)
 
select t.* , px = DENSE_RANK() over(partition by cid order by score desc) from sc t order by t.CID , px
 
#20、查询学生的总成绩并进行排名#20.1 查询学生的总成绩
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
order by 总成绩 desc
 
#20.2 查询学生的总成绩并进行排名，sql 2000用子查询完成，分总分重复时保留名次空缺和不保留名次空缺两种。
 
select t1.* , px = (select count(1) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t2 where 总成绩 > t1.总成绩) + 1 from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t1
 
order by px
 
select t1.* , px = (select count(distinct 总成绩) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t2 where 总成绩 >= t1.总成绩) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t1
 
order by px
 
#20.3 查询学生的总成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分总分重复时保留名次空缺和不保留名次空缺两种。
 
select t.* , px = rank() over(order by 总成绩 desc) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t
 
order by px
 
select t.* , px = DENSE_RANK() over(order by 总成绩 desc) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(sum(score),0) 总成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t
 
order by px
 
#21、查询不同老师所教不同课程平均分从高到低显示
 
select m.TID , m.Tname , cast(avg(o.score) as decimal(18,2)) avg_score
 
from Teacher m , Course n , SC o
 
where m.TID = n.TID and n.CID = o.CID
 
group by m.TID , m.Tname
 
order by avg_score desc
 
#22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩#22.1 sql 2000用子查询完成
 
#Score重复时保留名次空缺
 
select * from (select t.* , px = (select count(1) from SC where CID = t.CID and score > t.score) + 1 from sc t) m where px between 2 and 3 order by m.cid , m.px
 
#Score重复时合并名次
 
select * from (select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t) m where px between 2 and 3 order by m.cid , m.px
 
#22.2 sql 2005用rank,DENSE_RANK完成
 
#Score重复时保留名次空缺(rank完成)
 
select * from (select t.* , px = rank() over(partition by cid order by score desc) from sc t) m where px between 2 and 3 order by m.CID , m.px
 
#Score重复时合并名次(DENSE_RANK完成)
 
select * from (select t.* , px = DENSE_RANK() over(partition by cid order by score desc) from sc t) m where px between 2 and 3 order by m.CID , m.px
 
#23、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 , 0-60 及所占百分比 #23.1 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 , 0-60
 
#横向显示
 
select Course.CID 课程编号 , Cname as 课程名称 ,
 
sum(case when score >= 85 then 1 else 0 end) 85-100 ,
 
sum(case when score >= 70 and score < 85 then 1 else 0 end) 70-85 ,
 
sum(case when score >= 60 and score < 70 then 1 else 0 end) 60-70 ,
 
sum(case when score < 60 then 1 else 0 end) 0-60
 
from sc , Course
 
where SC.CID = Course.CID
 
group by Course.CID , Course.Cname
 
order by Course.CID
 
#纵向显示1(显示存在的分数段)
 
select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end) ,
 
count(1) 数量
 
from Course m , sc n
 
where m.CID = n.CID
 
group by m.CID , m.Cname , (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end)
 
order by m.CID , m.Cname , 分数段
 
#纵向显示2(显示存在的分数段，不存在的分数段用0显示)
 
select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end) ,
 
count(1) 数量
 
from Course m , sc n
 
where m.CID = n.CID
 
group by all m.CID , m.Cname , (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end)
 
order by m.CID , m.Cname , 分数段
 
#23.2 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 及所占百分比
 
#横向显示
 
select m.CID 课程编号, m.Cname 课程名称,
 
(select count(1) from SC where CID = m.CID and score < 60) 0-60 ,
 
cast((select count(1) from SC where CID = m.CID and score < 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,
 
(select count(1) from SC where CID = m.CID and score >= 60 and score < 70) 60-70 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 60 and score < 70)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,
 
(select count(1) from SC where CID = m.CID and score >= 70 and score < 85) 70-85 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 85)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,
 
(select count(1) from SC where CID = m.CID and score >= 85) 85-100 ,
 
cast((select count(1) from SC where CID = m.CID and score >= 85)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比
 
from Course m
 
order by m.CID
 
#纵向显示1(显示存在的分数段)
 
select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end) ,
 
count(1) 数量 ,
 
cast(count(1) * 100.0 / (select count(1) from sc where CID = m.CID) as decimal(18,2)) 百分比
 
from Course m , sc n
 
where m.CID = n.CID
 
group by m.CID , m.Cname , (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end)
 
order by m.CID , m.Cname , 分数段
 
#纵向显示2(显示存在的分数段，不存在的分数段用0显示)
 
select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end) ,
 
count(1) 数量 ,
 
cast(count(1) * 100.0 / (select count(1) from sc where CID = m.CID) as decimal(18,2)) 百分比
 
from Course m , sc n
 
where m.CID = n.CID
 
group by all m.CID , m.Cname , (
 
case when n.score >= 85 then '85-100'
 
when n.score >= 70 and n.score < 85 then '70-85'
 
when n.score >= 60 and n.score < 70 then '60-70'
 
else '0-60'
 
end)
 
order by m.CID , m.Cname , 分数段
 
#24、查询学生平均成绩及其名次#24.1 查询学生的平均成绩并进行排名，sql 2000用子查询完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。
 
select t1.* , px = (select count(1) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t2 where 平均成绩 > t1.平均成绩) + 1 from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t1
 
order by px
 
select t1.* , px = (select count(distinct 平均成绩) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t2 where 平均成绩 >= t1.平均成绩) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t1
 
order by px
 
#24.2 查询学生的平均成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。
 
select t.* , px = rank() over(order by 平均成绩 desc) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t
 
order by px
 
select t.* , px = DENSE_RANK() over(order by 平均成绩 desc) from
 
(
 
select m.SID 学生编号 ,
 
m.Sname 学生姓名 ,
 
isnull(cast(avg(score) as decimal(18,2)),0) 平均成绩
 
from Student m left join SC n on m.SID = n.SID
 
group by m.SID , m.Sname
 
) t
 
order by px
 
#25、查询各科成绩前三名的记录#25.1 分数重复时保留名次空缺
 
select m.* , n.CID , n.score from Student m, SC n where m.SID = n.SID and n.score in
 
(select top 3 score from sc where CID = n.CID order by score desc) order by n.CID , n.score desc
 
#25.2 分数重复时不保留名次空缺，合并名次
 
#sql 2000用子查询实现
 
select * from (select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t) m where px between 1 and 3 order by m.Cid , m.px
 
#sql 2005用DENSE_RANK实现
 
select * from (select t.* , px = DENSE_RANK() over(partition by Cid order by score desc) from sc t) m where px between 1 and 3 order by m.CID , m.px
 
#26、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
 
#27、查询出只有两门课程的全部学生的学号和姓名
 
select Student.SID , Student.Sname
 
from Student , SC
 
where Student.SID = SC.SID
 
group by Student.SID , Student.Sname
 
having count(SC.CID) = 2
 
order by Student.SID
 
#28、查询男生、女生人数
 
select count(Ssex) as 男生人数 from Student where Ssex = N'男'
 
select count(Ssex) as 女生人数 from Student where Ssex = N'女'
 
select sum(case when Ssex = N'男' then 1 else 0 end) 男生人数 ,sum(case when Ssex = N'女' then 1 else 0 end) 女生人数 from student
 
select case when Ssex = N'男' then N'男生人数' else N'女生人数' end 男女情况 , count(1) 人数 from student group by case when Ssex = N'男' then N'男生人数' else N'女生人数' end
 
#29、查询名字中含有"风"字的学生信息
 
select * from student where sname like N'%风%'
 
select * from student where charindex(N'风' , sname) > 0
 
#30、查询同名同性学生名单，并统计同名人数
 
select Sname 学生姓名 , count(*) 人数 from Student group by Sname having count(*) > 1
 
#31、查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)
 
select * from Student where year(sage) = 1990
 
select * from Student where datediff(yy,sage,'1990-01-01') = 0
 
select * from Student where datepart(yy,sage) = 1990
 
select * from Student where convert(varchar(4),sage,120) = '1990'
 
#32、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 m.CID , m.Cname , cast(avg(n.score) as decimal(18,2)) avg_score
 
from Course m, SC n
 
where m.CID = n.CID
 
group by m.CID , m.Cname
 
order by avg_score desc, m.CID asc
 
#33、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 a.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score
 
from Student a , sc b
 
where a.SID = b.SID
 
group by a.SID , a.Sname
 
having cast(avg(b.score) as decimal(18,2)) >= 85
 
order by a.SID
 
#34、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 Student , SC , Course
 
where SC.SID = Student.SID and SC.CID = Course.CID and Course.Cname = N'数学' and score < 60
 
#35、查询所有学生的课程及分数情况
 
select Student.* , Course.Cname , SC.CID , SC.score
 
from Student, SC , Course
 
where Student.SID = SC.SID and SC.CID = Course.CID
 
order by Student.SID , SC.CID
 
#36、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 Student.* , Course.Cname , SC.CID , SC.score
 
from Student, SC , Course
 
where Student.SID = SC.SID and SC.CID = Course.CID and SC.score >= 70
 
order by Student.SID , SC.CID
 
#37、查询不及格的课程
 
select Student.* , Course.Cname , SC.CID , SC.score
 
from Student, SC , Course
 
where Student.SID = SC.SID and SC.CID = Course.CID and SC.score < 60
 
order by Student.SID , SC.CID
 
#38、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.* , Course.Cname , SC.CID , SC.score
 
from Student, SC , Course
 
where Student.SID = SC.SID and SC.CID = Course.CID and SC.CID = '01' and SC.score >= 80
 
order by Student.SID , SC.CID
 
#39、求每门课程的学生人数
 
select Course.CID , Course.Cname , count(*) 学生人数
 
from Course , SC
 
where Course.CID = SC.CID
 
group by Course.CID , Course.Cname
 
order by Course.CID , Course.Cname
 
#40、查询选修"李零"老师所授课程的学生中，成绩最高的学生信息及其成绩#40.1 当最高分只有一个时
 
select top 1 Student.* , Course.Cname , SC.CID , SC.score
 
from Student, SC , Course , Teacher
 
where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'李零'
 
order by SC.score desc
 
#40.2 当最高分出现多个时
 
select Student.* , Course.Cname , SC.CID , SC.score
 
from Student, SC , Course , Teacher
 
where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'李零' and
 
SC.score = (select max(SC.score) from SC , Course , Teacher where SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'李零')
 
#41、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
 
#方法1
 
select m.* from SC m ,(select CID , score from SC group by CID , score having count(1) > 1) n
 
where m.CID= n.CID and m.score = n.score order by m.CID , m.score , m.SID
 
#方法2
 
select m.* from SC m where exists (select 1 from (select CID , score from SC group by CID , score having count(1) > 1) n
 
where m.CID= n.CID and m.score = n.score) order by m.CID , m.score , m.SID
 
#42、查询每门功成绩最好的前两名
 
select t.* from sc t where score in (select top 2 score from sc where CID = T.CID order by score desc) order by t.CID , t.score desc
 
#43、统计每门课程的学生选修人数（超过5人的课程才统计）。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 , Course.Cname , count(*) 学生人数
 
from Course , SC
 
where Course.CID = SC.CID
 
group by Course.CID , Course.Cname
 
having count(*) >= 5
 
order by 学生人数 desc , Course.CID
 
#44、检索至少选修两门课程的学生学号
 
select student.SID , student.Sname
 
from student , SC
 
where student.SID = SC.SID
 
group by student.SID , student.Sname
 
having count(1) >= 2
 
order by student.SID
 
#45、查询选修了全部课程的学生信息
 
#方法1 根据数量来完成
 
select student.* from student where SID in
 
(select SID from sc group by SID having count(1) = (select count(1) from course))
 
#方法2 使用双重否定来完成
 
select t.* from student t where t.SID not in
 
(
 
select distinct m.SID from
 
(
 
select SID , CID from student , course
 
) m where not exists (select 1 from sc n where n.SID = m.SID and n.CID = m.CID)
 
)
 
#方法3 使用双重否定来完成
 
select t.* from student t where not exists(select 1 from
 
(
 
select distinct m.SID from
 
(
 
select SID , CID from student , course
 
) m where not exists (select 1 from sc n where n.SID = m.SID and n.CID = m.CID)
 
) k where k.SID = t.SID
 
)
 
#46、查询各学生的年龄#46.1 只按照年份来算
 
select * , datediff(yy , sage , getdate()) 年龄 from student
 
#46.2 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 * , case when right(convert(varchar(10),getdate(),120),5) < right(convert(varchar(10),sage,120),5) then datediff(yy , sage , getdate()) - 1 else datediff(yy , sage , getdate()) end 年龄 from student
 
#47、查询本周过生日的学生
 
select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0
 
#48、查询下周过生日的学生
 
select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1
 
#49、查询本月过生日的学生
 
select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0
 
#50、查询下月过生日的学生
 
select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1