---恢復內容開始---
問題及描述：
--1.學生表
Student(SID,Sname,Sage,Ssex) --SID 學生編號,Sname 學生姓名,Sage 出生年月,Ssex 學生性別
--2.課程表
Course(CID,Cname,TID) --CID --課程編號,Cname 課程名稱,TID 教師編號
--3.教師表
Teacher(TID,Tname) --TID 教師編號,Tname 教師姓名
--4.成績表
SC(SID,CID,score) --SID 學生編號,CID 課程編號,score 分數
*/
--創建測試數據
create table Student(SID varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10));
insert into Student values('01' , '趙雷' , '1990-01-01' , '男');
insert into Student values('02' , '錢電' , '1990-12-21' , '男');
insert into Student values('03' , '孫風' , '1990-05-20' , '男');
insert into Student values('04' , '李雲' , '1990-08-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吳蘭' , '1992-03-01' , '女');
insert into Student values('07' , '鄭竹' , '1989-07-01' , '女');
insert into Student values('08' , '王菊' , '1990-01-20' , '女');
create table Course(CID varchar(10),Cname nvarchar(10),TID varchar(10));
insert into Course values('01' , '語文' , '02');
insert into Course values('02' , '數學' , '01');
insert into Course values('03' , '英語' , '03');
create table Teacher(TID varchar(10),Tname nvarchar(10));
insert into Teacher values('01' , '張三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');
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、查詢"01"課程比"02"課程成績高的學生的信息及課程分數
--1.1、查詢同時存在"01"課程和"02"課程的情況
select a.* , b.score 課程01的分數,c.score 課程02的分數 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;
--1.2、查詢同時存在"01"課程和"02"課程的情況和存在"01"課程但可能不存在"02"課程的情況(不存在時顯示為null)(以下存在相同內容時不再解釋)
select a.* , b.score 課程01的分數,c.score 課程02的分數 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 b.score > isnull(c.score);
--2、查詢"01"課程比"02"課程成績低的學生的信息及課程分數
--2.1、查詢同時存在"01"課程和"02"課程的情況
select a.* , b.score 課程01的分數 ,c.score 課程02的分數 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、查詢同時存在"01"課程和"02"課程的情況和不存在"01"課程但存在"02"課程的情況
select a.* , b.score 課程01的分數 ,c.score 課程02的分數 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 isnull(b.score) < c.score;
如要顯示沒選課的學生(顯示為NULL)，需要使用join:
--3、查詢平均成績大於等於60分的同學的學生編號和學生姓名和平均成績
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;
CAST函數用於將某種數據類型的表達式顯式轉換為另一種數據類型。CAST()函數的參數是一個表達式，它包括用AS關鍵字分隔的源值和目標數據類型。
CAST (expression AS data_type)；
decimal(a,b)
a指定指定小數點左邊和右邊可以存儲的十進制數字的最大個數，最大精度38。
b指定小數點右邊可以存儲的十進制數字的最大個數。小數位數必須是從 0 到 a之間的值。默認小數位數是 0。
--4、查詢平均成績小於60分的同學的學生編號和學生姓名和平均成績
--4.1、查詢在sc表存在成績的學生信息的SQL語句。
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
67--4.2、查詢在sc表中不存在成績的學生信息的SQL語句(有成績不等於學生信息在sc表里)。
select a.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score
from Student a left join sc b
on a.SID = b.SID
group by a.SID , a.Sname
having cast(avg(b.score) as decimal(18,2)) < 60
order by a.SID;
--5、查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績
--5.1、查詢所有有成績的SQL。
select a.SID 學生編號 , a.Sname 學生姓名 , count(b.CID) 選課總數, sum(score) 所有課程的總成績
from Student a , SC b
where a.SID = b.SID
group by a.SID,a.Sname
order by a.SID
--5.2、查詢所有(包括有成績和無成績)的SQL。
select a.SID 學生編號 , a.Sname 學生姓名 , count(b.CID) 選課總數, sum(score) 所有課程的總成績
from Student a left join SC b
on a.SID = b.SID
group by a.SID,a.Sname
order by a.SID
--6、查詢"李"姓老師的數量
--方法1
select count(Tname) 李姓老師的數量 from Teacher where Tname like '李%'
--方法2
select count(Tname) 李姓老師的數量 from Teacher where left(Tname,1) = '李'
--7、查詢學過"張三"老師授課的同學的信息
select distinct Student.* from Student , SC , Course , Teacher
where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = '張三'
order by Student.SID
--8、查詢沒學過"張三"老師授課的同學的信息
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 = '張三') order by m.SID
--9、查詢學過編號為"01"並且也學過編號為"02"的課程的同學的信息
--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、查詢學過編號為"01"但是沒有學過編號為"02"的課程的同學的信息
--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、查詢沒有學全所有課程的同學的信息
--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、查詢至少有一門課與學號為"01"的同學所學相同的同學的信息
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、查詢和"01"號的同學學習的課程完全相同的其他同學的信息
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、查詢沒學過"張三"老師講授的任一門課程的學生姓名
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 = '張三')
order by student.SID
--15、查詢兩門及其以上不及格課程的同學的學號，姓名及其平均成績
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、檢索"01"課程分數小於60，按分數降序排列的學生信息
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、按平均成績從高到低顯示所有學生的所有課程的成績以及平均成績
--17.1 SQL 2000 靜態
select a.SID 學生編號 , a.Sname 學生姓名 ,
max(case c.Cname when '語文' then b.score else null end) 語文 ,
max(case c.Cname when '數學' then b.score else null end) 數學 ,
max(case c.Cname when '英語' then b.score else null end) 英語 ,
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 動態
declare @sql nvarchar(4000)
set @sql = 'select a.SID ' + '學生編號' + ' , a.Sname ' + '學生姓名'
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、查詢各科成績最高分、最低分和平均分：以如下形式顯示：課程ID，課程name，最高分，最低分，平均分，及格率，中等率，優良率，優秀率
--及格為>=60，中等為：70-80，優良為：80-90，優秀為：>=90
--方法1
select m.CID 課程編號 , m.Cname 課程名稱 ,
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)) 優良率 ,
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)) 優秀率
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 課程編號 , m.Cname 課程名稱 ,
(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)) 優良率 ,
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)) 優秀率
from Course m
order by m.CID
--19、按各科成績進行排序，並顯示排名
--19.1 sql 2000用子查詢完成
--Score重復時保留名次空缺
select t.* , (select count(1) from SC where CID = t.CID and score > t.score) + 1 px from sc t order by t.cid , px;
方法二（推薦）：
select t.* , (select count( score) from SC where CID = t.CID and score > t.score) +1 px from sc t order by t.cid , px;
--Score重復時合並名次
select t.* , (select count(distinct score) from SC where CID = t.CID and score >= t.score) px from sc t order by t.cid , px;
方法二（推薦）：
select t.* , (select count(distinct score) from SC where CID = t.CID and score > t.score) +1 px from sc t order by t.cid , px;
--19.2 sql 2005用rank,DENSE_RANK完成
--Score重復時保留名次空缺(rank完成)
select t.* , px = rank() over(partition by cid order by score desc) from sc t order by t.CID , px
--Score重復時合並名次(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、查詢學生的總成績並進行排名
--20.1 查詢學生的總成績
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
sum(score) 總成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
order by 總成績 desc;
--20.2 查詢學生的總成績並進行排名，sql 2000用子查詢完成，分總分重復時保留名次空缺和不保留名次空缺兩種。
select t1.* , px = (select count(1) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(sum(score),0) 總成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t2 where 總成績 > t1.總成績) + 1 from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(sum(score),0) 總成績
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 總成績) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(sum(score),0) 總成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t2 where 總成績 >= t1.總成績) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(sum(score),0) 總成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t1
order by px
--20.3 查詢學生的總成績並進行排名，sql 2005用rank,DENSE_RANK完成，分總分重復時保留名次空缺和不保留名次空缺兩種。
select t.* , px = rank() over(order by 總成績 desc) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(sum(score),0) 總成績
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 總成績 desc) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(sum(score),0) 總成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t
order by px
--21、查詢不同老師所教不同課程平均分從高到低顯示
select m.TID ,n.Cname, 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, n.Cname , m.Tname
order by avg_score desc;
--22、查詢所有課程的成績第2名到第3名的學生信息及該課程成績
--22.1 sql 2000用子查詢完成
--Score重復時保留名次空缺
方法一：select * from (select t.* , (select count(1) from SC where CID = t.CID and score > t.score) + 1 px from sc t) m where px between 2 and 3 order by m.cid;
方法二（推薦）：select t.*,(select count(score) from sc where cid=t.cid and score>t.score) +1 px from sc t having px>=2 and px<=3 order by t.cid,px;
--Score重復時合並名次
方法一：select * from (select t.* , (select count(distinct score) from SC where CID = t.CID and score >= t.score) px from sc t) m where px between 2 and 3 order by m.cid;
方法二（推薦）：select t.* , (select count(distinct score) from SC where CID = t.CID and score > t.score) + 1 px from sc t having px>=2 and px<=3 order by t.cid , px;
--22.2 sql 2005用rank,DENSE_RANK完成
--Score重復時保留名次空缺(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重復時合並名次(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、統計各科成績各分數段人數：課程編號,課程名稱, 100-85 , 85-70 , 70-60 , 0-60 及所占百分比
--23.1 統計各科成績各分數段人數：課程編號,課程名稱, 100-85 , 85-70 , 70-60 , 0-60
--橫向顯示
select Course.CID 課程編號 , Cname as 課程名稱 ,
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;
--縱向顯示1(顯示存在的分數段)
select m.CID 課程編號 , m.Cname 課程名稱 , (
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) 分數段 ,
count(1) 數量
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 , 分數段;
--縱向顯示2(顯示存在的分數段，不存在的分數段用0顯示)
select m.CID 課程編號 , m.Cname 課程名稱 , (
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) 分數段,
count(1) 數量
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 , 分數段;
--23.2 統計各科成績各分數段人數：課程編號,課程名稱, 100-85 , 85-70 , 70-60 , <60 及所占百分比
--橫向顯示
select m.CID 課程編號, m.Cname 課程名稱,
(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;
--縱向顯示1(顯示存在的分數段)
select m.CID 課程編號 , m.Cname 課程名稱 , (
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) 分數段,
count(1) 數量 ,
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 , 分數段;
--縱向顯示2(顯示存在的分數段，不存在的分數段用0顯示)
select m.CID 課程編號 , m.Cname 課程名稱 ,(
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) 分數段,
count(1) 數量 ,
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 , 分數段;
--24、查詢學生平均成績及其名次
--24.1 查詢學生的平均成績並進行排名，sql 2000用子查詢完成，分平均成績重復時保留名次空缺和不保留名次空缺兩種。
方法一（推薦）：
select a.sid 學生編號,a.sname 學生姓名,cast(avg(b.score) as decimal(18,2)) 平均成績,
(select count(*) from sc where sc.cid=b.cid and sc.score>=b.score)+1 px
from student a left join sc b on a.sid=b.sid group by a.sid,a.sname order by px;
select t1.* , (select count(1) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
cast(avg(score) as decimal(18,2)) 平均成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t2 where 平均成績 > t1.平均成績) + 1 px from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
cast(avg(score) as decimal(18,2)) 平均成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t1
order by px;
--24.2 查詢學生的平均成績並進行排名，sql 2005用rank,DENSE_RANK完成，分平均成績重復時保留名次空缺和不保留名次空缺兩種。
select t.* , px = rank() over(order by 平均成績 desc) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(cast(avg(score) as decimal(18,2)),0) 平均成績
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 平均成績 desc) from
(
select m.SID 學生編號 ,
m.Sname 學生姓名 ,
isnull(cast(avg(score) as decimal(18,2)),0) 平均成績
from Student m left join SC n on m.SID = n.SID
group by m.SID , m.Sname
) t
order by px
--25、查詢各科成績前三名的記錄
--25.1 分數重復時保留名次空缺
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
SELECT a.*,COUNT(B.score) +1 as ranking
FROM SC a LEFT JOIN SC b
ON a.CId = b.CId AND a.score<b.score
GROUP BY a.CId,a.SId,a.score
HAVING ranking <= 3
ORDER BY a.CId,ranking;
--25.2 分數重復時不保留名次空缺，合並名次
--sql 2000用子查詢實現
select * from (select t.* , (select count(distinct score) from SC where CID = t.CID and score >= t.score) px from sc t) m where px between 1 and 3 order by m.Cid , m.px;
--sql 2005用DENSE_RANK實現
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、查詢每門課程被選修的學生數
select sc.Cid,course.Cname , count(SID) 學生數 from course,sc where course.cid=sc.cid group by CID;
--27、查詢出只有兩門課程的全部學生的學號和姓名
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、查詢男生、女生人數
select count(Ssex) as 男生人數 from Student where Ssex = N'男'
select count(Ssex) as 女生人數 from Student where Ssex = N'女'
select sum(case when Ssex = N'男' then 1 else 0 end) 男生人數 ,sum(case when Ssex = N'女' then 1 else 0 end) 女生人數 from student
select case when Ssex = N'男' then N'男生人數' else N'女生人數' end 男女情況 , count(1) 人數 from student group by case when Ssex = N'男' then N'男生人數' else N'女生人數' end;
--29、查詢名字中含有"風"字的學生信息
select * from student where sname like N'%風%';
--30、查詢同名同性學生名單，並統計同名人數
select Sname 學生姓名 , count(*) 人數 from Student group by Sname having count(*) > 1;
--31、查詢1990年出生的學生名單(注：Student表中Sage列的類型是datetime)
select * from student where Sage like '1990%';
select * from Student where year(sage) = 1990;
--32、查詢每門課程的平均成績，結果按平均成績降序排列，平均成績相同時，按課程編號升序排列
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、查詢平均成績大於等於85的所有學生的學號、姓名和平均成績
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、查詢課程名稱為"數學"，且分數低於60的學生姓名和分數
select sname , score
from Student , SC , Course
where SC.SID = Student.SID and SC.CID = Course.CID and Course.Cname = N'數學' and score < 60;
--35、查詢所有學生的課程及分數情況；
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、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數；
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、查詢不及格的課程
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、查詢課程編號為01且課程成績在80分以上的學生的學號和姓名；
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、求每門課程的學生人數
select Course.CID , Course.Cname,count(1) 學生人數
from course,sc
where course.cid=sc.CID
group by Course.CID , Course.Cname
order by Course.CID , Course.Cname;
方法二：
select CId,count(SId)
from sc group by sc.CId
--40、查詢選修"張三"老師所授課程的學生中，成績最高的學生信息及其成績
--40.1 當最高分只有一個時
sSELECT Student.*,SC.CId,score
FROM Student JOIN SC ON Student.SId = SC.SId
JOIN Course ON SC.CId = Course.CId
JOIN Teacher ON Course.TId = Teacher.TId
WHERE Tname = '張三'
ORDER BY score DESC LIMIT 1;
--40.2 當最高分出現多個時
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'張三' 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'張三')；
SELECT Student.*,SC.CId,score
FROM Student JOIN SC ON Student.SId = SC.SId
JOIN Course ON SC.CId = Course.CId
JOIN Teacher ON Course.TId = Teacher.TId
WHERE Tname = '張三' AND score IN
(SELECT MAX(score) FROM
SC JOIN Course ON SC.CId = Course.CId
JOIN Teacher ON Course.TId = Teacher.TId
WHERE Tname = '張三');
--41、查詢不同課程成績相同的學生的學生編號、課程編號、學生成績
--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、查詢每門功成績最好的前兩名
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、統計每門課程的學生選修人數（超過5人的課程才統計）。要求輸出課程號和選修人數，查詢結果按人數降序排列，若人數相同，按課程號升序排列
select Course.CID , Course.Cname , count(*) 學生人數
from Course , SC
where Course.CID = SC.CID
group by Course.CID , Course.Cname
having count(*) >= 5
order by 學生人數 desc , Course.CID;
--44、檢索至少選修兩門課程的學生學號
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、查詢選修了全部課程的學生信息
--方法1 根據數量來完成
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 使用雙重否定來完成
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 使用雙重否定來完成
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、查詢各學生的年齡
--46.1 只按照年份來算
select * , datediff(yy , sage , getdate()) 年齡 from student
select Sname,Sage,
year(now())-year(Sage) as 年齡
from student;
--46.2 按照出生日期來算，當前月日 < 出生年月的月日則，年齡減一
SELECT SId,Sname,TIMESTAMPDIFF(YEAR,Sage,NOW()) AS 年齡
FROM Student;
--47、查詢本周過生日的學生
SELECT * FROM student where
week(Sage)=week(now());
--48、查詢下周過生日的學生
SELECT * FROM student where
week(Sage)=week(now())+1;
--49、查詢本月過生日的學生
SELECT * FROM student
where month(Sage)=month(now());
--50、查詢下月過生日的學生
SELECT * FROM student
where month(Sage)=month(now())+1;
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