SQL 練習題50道

首先是建立練習使用各種表格（這里使用的是SQL server建立的）：

use school;
-- 創建學生表
create table Student(
    Sno varchar(20),
    Sname varchar(20) not null,
    Ssex varchar(20) not null,
    Sbirthday datetime,
    Class varchar(20)    
);
-- 創建教師表
create table Teacher(
    Tno varchar(20),
    Tname varchar(20) not null,
    Tsex varchar(20) not null,
    Tbrithday datetime,
    Prof varchar(20),
    Depart varchar(20) not null

);
-- 創建課程表
create table Course(
    Cno varchar(20),
    Cname varchar(20) not null,
    Tno varchar(20) not null,
);
-- 創建成績表
create table Score(
    Sno varchar(20) not null,
    Cno varchar(20) not null,
    -- 成績
    Degree Decimal
);

--添加約束
--為學生表添加約束,把列Sno作為主鍵約束,把列Ssex添加檢查約束
alter table Student
add constraint CK_Sno check(Sno is not null),  --為列Sno添加非空約束
    constraint PK_Sno primary key(Sno),        --為列Sno添加主鍵約束
    constraint CK_Ssex check(Ssex='男' or Ssex='女')  --為列Ssex添加檢查約束，令列Ssex列只能輸入男或女
--為課程表添加約束
alter table Course 
add constraint CK_Cno check(Cno is not null),
    constraint PK_Cno primary key(Cno), --為列Cno添加主鍵約束
    constraint UQ_Cname unique(Cname)  --為列Cname添加唯一約束


--為教師表格添加約束，為列Tno添加主鍵約束，為列Tsex添加檢查約束,為列Depart添加外鍵約束
alter table Teacher 
add constraint CK_Tno check(Tno is not null),
    constraint PK_Tno primary key(Tno),  --為列Tno添加主鍵約束
    constraint CK_Tsex check(Tsex='男' or Tsex='女')  --為列Tsex添加檢查約束

go
--添加數據
-- 添加學生信息
insert into student values('108','曾華','男','1977-09-01','95033');
insert into student values('105','匡明','男','1975-10-02','95031');
insert into student values('107','王麗','女','1976-01-23','95033');
insert into student values('101','李軍','男','1976-02-20','95033');
insert into student values('109','王芳','女','1975-02-10','95031');
insert into student values('103','陸君','男','1974-06-03','95031');

-- 添加教師信息
insert into teacher values('804','李誠','男','1958-12-02','副教授','計算機系');
insert into teacher values('856','張旭','男','1969-03-12','講師','電子工程系');
insert into teacher values('825','王萍','女','1972-05-05','助教','計算機系');
insert into teacher values('831','劉冰','女','1977-08-14','助教','電子工程系');

-- 添加課程信息
insert into course values('3-105','計算機導論','825');
insert into course values('3-245','操作系統','804');
insert into course values('6-166','數字電路','856');
insert into course values('9-888','高等數學','831');

-- 添加成績信息
insert into score values('103','3-245','86');
insert into score values('105','3-245','75');
insert into score values('109','3-245','68');
insert into score values('103','3-105','92');
insert into score values('105','3-105','88');
insert into score values('109','3-105','76');
-- insert into score values('103','3-105','64');
-- insert into score values('105','3-105','91');
-- insert into score values('109','3-105','78');
-- 這三行數據在樣例里面給出，但是主鍵重復了。- -，報錯嚇了我一跳
insert into score values('103','6-166','85');
insert into score values('105','6-166','79');
insert into score values('109','6-166','81')
go

接下來是練習題及答案：

--1、 查詢Student表中的所有記錄的Sname、Ssex和Class列。
select Sname, Ssex, Class from Student
--2、 查詢教師所有的單位即不重復的Depart列。
select distinct Depart,Tname from Teacher
--3、查詢Student表的所有記錄。
select * from Student
--4、查詢Score表中成績在60到80之間的所有記錄
select * from Score
where Degree between 60 and 80
--5、查詢Score表中成績為85，86或88的記錄。
select * from Score
where Degree in (85,86,88)
--6、查詢Student表中“95031”班或性別為“女”的同學記錄。
select * from Student
where Ssex='女' or Class='95031'

--7、以Class降序查詢Student表的所有記錄。
select * from Student order by Class desc
--8、以Cno升序、Degree降序查詢Score表的所有記錄。
select * from Score order by Cno,Degree desc   --多個條件用","來分隔
--9、查詢“95031”班的學生人數。
select count(*) from Student
where Class='95031'

--10、 查詢Score表中的最高分的學生學號和課程號。（子查詢或者排序）
select Sno,Cno from Score
where Degree = (select max(degree) from score)
select top 1 Sno,Cno from Score
order by Degree desc


--11、查詢每門課的平均成績，要按照課程分組group by，然后求沒門課平均avg
select Cno, convert(numeric(18,2),avg(Degree)) 平均成績 from Score
group by Cno
--12、查詢Score表中至少有5名學生選修的並以3開頭的課程的平均分數。
select Cno,avg(Degree) from Score
group by Cno
having  Cno like '3%' and Cno in (select Cno from Score group by Cno having count(Cno) > 2)
--Like模糊查詢     3%以3開頭    having只能跟在group by 后面
--13、查詢分數大於70，小於90的Sno列。

select Sno from Score
where Degree between 70 and 90
--14、查詢所有學生的Sname、Cno和Degree列。
select A.Sno,A.Degree,B.Sname from Score as A 
inner join Student as B
on A.Sno = B.Sno
--15、查詢所有學生的Sno、Cname和Degree列。
select A.Sno,A.Degree,C.Cname from Score as A 
inner join Course as C
on A.Cno = C.Cno
go
--16、查詢所有學生的Sname、Cname和Degree列。
select S.Sname,A.Degree,C.Cname from Score as A 
inner join Course as C
on A.Cno = C.Cno
inner join Student as S
on S.Sno=A.Sno
go
--17、 查詢“95033”班學生的平均分。
select S.Class as 班級 ,avg(A.Degree) as 評分分 from Score as A
inner join Student as S
on S.Sno = A.Sno
group by S.Class

--建立新表grade表
create table grade 
(low  int,upp  int,ranks  char(1))
insert into grade values(90,100,'A')

insert into grade values(80,89,'B')

insert into grade values(70,79,'C')

insert into grade values(60,69,'D')

insert into grade values(0,59,'E')
select * from grade
--現查詢所有同學的Sno、Cno和rank列。
--方法一
select * , (select ranks from grade where low < Degree and Upp >= Degree) as 評級
from Score
方法二
select A.* , G.ranks from Score as A 
inner join grade as G
on A.Degree between G.low and G.upp

--19、  查詢選修“3-105”課程的成績高於“109”號同學成績的所有同學的記錄。
select * from Score 
where Degree > (select Degree from Score where Sno='109' and Cno = '3-105') and  Cno = '3-105'

--20、查詢score中選學多門課程的同學中分數為非最高分成績的記錄。
Select * from score a 
where degree <(select max(degree) from Score b where b.Cno=a.Cno) 
and Sno in (select Sno from Score group by Sno having count(*)>1)

--結合條件一定要寫在子查詢中,子查詢內部設定的關聯名稱,只能在該子查詢內部使用,也就是說內部可以看到外部,而
--外部看不到內部
--SQL是按照先內層子查詢后補外層查詢的順序來執行的,這樣,子查詢執行結束后只會留下執行結果.

--22、查詢和學號為105的同學同年出生的所有學生的Sno、Sname和Sbirthday列。
select * from Score AS A
inner join Student AS S
on A.Sno=S.Sno
where year(S.Sbirthday) = (select year(Sbirthday) from Student where Sno='105')
--23、查詢“張旭“教師任的學生成績。
select A.* from Teacher as T
inner join Course as C
on T.Tno=C.Tno
inner join Score AS A
on A.Cno=C.Cno
where T.Tname='張旭'

--24、查詢選修某課程的同學人數多於5人的教師姓名。
select A.Cno,T.Tname,Count(A.Cno) from Teacher as T
inner join Course as C
on T.Tno=C.Tno
inner join Score AS A
on A.Cno=C.Cno
group by A.Cno,T.Tname

--25、查詢95033班和95031班全體學生的記錄。
select * from Student
where Class='95033' or Class='95031'
--26、  查詢存在有85分以上成績的課程Cno.
select Cno from Score 
where Degree > 85
group by Cno

--27、查詢出“計算機系“教師所教課程的成績表。
select A.* from Teacher as T
inner join Course as C
on T.Tno=C.Tno
inner join Score AS A
on A.Cno=C.Cno
where T.Depart='計算機系'


--28、查詢“計算機系”與“電子工程系“不同職稱的教師的Tname和Prof。?
select Prof,Depart from Teacher as a
where Prof not in (select Prof from Teacher as b where b.Depart <> a.Depart)

--29、查詢選修編號為“3-105“課程且成績至少高於選修編號為“3-245”的同學的記錄
select * from Score as A
inner join Student as S
on A.Sno = S.Sno
where Cno = '3-105' and Degree > (select Degree from Score as B where B.Sno=A.Sno and B.Cno='3-245')

--31、 查詢所有教師和同學的name、sex和birthday.
select Sname, Ssex, convert(date,Sbirthday) from Student
union (select Tname,Tsex,convert(date,Tbrithday) from Teacher)

--32、查詢所有“女”教師和“女”同學的name、sex和birthday.
select Sname as name, Ssex as sex, convert(date,Sbirthday) as birthday from Student
where Ssex='女'
union (select Tname,Tsex,convert(date,Tbrithday) from Teacher where Tsex='女')

--33、 查詢成績比該課程平均成績低的同學的成績表。
select * from Score as a
where Degree < (select avg(Degree) from Score as b where b.Cno=a.Cno group by b.Cno)

--34、查詢所有任課教師的Tname和Depart.
select Tname,Depart from Teacher 
--35 、查詢所有未講課的教師的Tname和Depart.
select * from Teacher 
where Tno not in (select Tno from Course where Cno in (select Cno from Score))
--36、查詢至少有2名男生的班號。
select Class from Student
where Ssex='男'
group by Class
having Count(Class)>=2
--37.查詢不姓王的同學信息
select * from Student
where Sname not like '王%'
--38、查詢Student表中每個學生的姓名和年齡。
select Sname,Ssex from Student
--39、查詢Student表中最大和最小的Sbirthday日期值。
select max(Sbirthday) as 最大日期值,min(Sbirthday) as 最小日期值 from Student
--40、以班號和年齡從大到小的順序查詢Student表中的全部記錄。
select * from Student
order by Class,Sbirthday desc
--41、查詢“男”教師及其所上的課程。
select T.Tname, C.Cno from Teacher as T
inner join Course as C
on T.Tno=C.Tno
where T.Tsex='男'
--42、查詢最高分同學的Sno、Cno和Degree列。
select * from Score
where Degree =(select max(Degree) from Score )
--43、查詢和“李軍”同性別的所有同學的Sname.
select Sname from Student
where Ssex=(select Ssex from Student where Sname='李軍') and Sname <> '李軍'
--44、查詢和“李軍”同性別並同班的同學Sname.

select Sname from Student
where Ssex=(select Ssex from Student where Sname='李軍') and Sname <> '李軍' 
and Class = (select Class from Student where Sname='李軍')
--45、查詢所有選修“計算機導論”課程的“男”同學的成績表。SQL語句
select * from Score
where Sno in (select Sno from Student where Ssex='男') and Cno in (select Cno from Course where Cname='計算機導論')

--46,查詢" 3-245 "課程比" 3-105 "課程成績高的學生的信息及課程分數
select * from Score as A
inner join Score as B
on A.Sno = B.Sno
where A.Cno='3-245' and B.Cno='3-105' and A.Degree < B.Degree
--47.查詢各科成績的最高分及最低分及格率，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

--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 Cno as 科目, Max(Degree) as 最高分, MIn(Degree) as 最低分, convert(int,avg(Degree)) as 平均分 ,
convert(varchar(20),convert(numeric(10,2),convert(numeric(10,2),sum(case when Degree >= 60 then 1 else 0 end))/Count(Cno)*100)) + '%' as 及格率,
convert(varchar(20),convert(numeric(10,2),convert(numeric(10,2),sum(case when Degree >= 70 and Degree <80 then 1 else 0 end))/Count(Cno)*100)) + '%' as 中等率,
convert(varchar(20),convert(numeric(10,2),convert(numeric(10,2),sum(case when Degree >=80 and Degree < 90 then 1 else 0 end))/Count(Cno)*100)) + '%' as 優良率,
convert(varchar(20),convert(numeric(10,2),convert(numeric(10,2),sum(case when Degree >= 60 then 1 else 0 end))/Count(Cno)*100) )+ '%' as 優秀率
from Score 
group by Cno
order by count(Cno),Cno
--48.按各科成績進行排序，並顯示排名， degree 重復時保留名次空缺
select * , rank() over(partition by Cno order by Degree) as 排名 from Score

--49查詢各科成績前兩名的記錄
select * from(select * , rank() over(partition by Cno order by Degree) as 排名 from Score) as A
where A.排名 <=2
--50查詢所有學生的課程及分數情況（存在學生沒成績，沒選課的情況）
select S.Sno,A.* from Student as S
left join Score as A
on S.Sno=A.Sno
--51.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
select * from Score as A
inner join Score as B
on A.Sno = B.Sno
where A.Cno <> B.Cno and A.Degree = B.Degree