SQL 45道題

數(shù)據(jù)表

1.學(xué)生表 Student(SId,Sname,Sage,Ssex)

SId 學(xué)生編號(hào),Sname 學(xué)生姓名,Sage 出生年月,Ssex 學(xué)生性別

2.課程表 Course(CId,Cname,TId)

CId --課程編號(hào),Cname 課程名稱(chēng),TId 教師編號(hào)

3.教師表 Teacher(TId,Tname)

TId 教師編號(hào),Tname 教師姓名

4.成績(jī)表 SC(SId,CId,score)

SId 學(xué)生編號(hào),CId 課程編號(hào),score 分?jǐn)?shù)

創(chuàng)建測(cè)試數(shù)據(jù)

學(xué)生表 Student

create table Student(SId varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10));
insert into Student values('01' , '趙雷' , '1990-01-01' , '男');
insert into Student values('02' , '錢(qián)電' , '1990-12-21' , '男');
insert into Student values('03' , '孫風(fēng)' , '1990-05-20' , '男');
insert into Student values('04' , '李云' , '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('09' , '張三' , '2017-12-20' , '女');
insert into Student values('10' , '李四' , '2017-12-25' , '女');
insert into Student values('11' , '李四' , '2017-12-30' , '女');
insert into Student values('12' , '趙六' , '2017-01-01' , '女');
insert into Student values('13' , '孫七' , '2018-01-01' , '女');

科目表 Course

create table Course(CId varchar(10),Cname nvarchar(10),TId varchar(10));
insert into Course values('01' , '語(yǔ)文' , '02');
insert into Course values('02' , '數(shù)學(xué)' , '01');
insert into Course values('03' , '英語(yǔ)' , '03');

教師表 Teacher

create table Teacher(TId varchar(10),Tname varchar(10));
insert into Teacher values('01' , '張三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');

成績(jī)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)

練習(xí)題目

1.查詢" 01 "課程比" 02 "課程成績(jī)高的學(xué)生的信息及課程分?jǐn)?shù)

#查詢" 01 "課程的學(xué)生
SELECT SId,score FROM SC
WHERE CId=01
#查詢" 02 "課程的學(xué)生
SELECT SId,score FROM SC
WHERE CId=02
#查詢" 01 "課程比" 02 "課程成績(jī)高的學(xué)生
SELECT *
FROM 
(SELECT * FROM SC
WHERE CId='01') A
JOIN
(SELECT * FROM SC
WHERE CId='02') B
ON A.SId=B.SId
WHERE A.score>B.score

#簡(jiǎn)化查詢表格
SELECT A.SId,A.score class01,B.score class02
FROM (SELECT * FROM SC
WHERE CId='01') A
JOIN
(SELECT * FROM SC
WHERE CId='02') B
ON A.SId=B.SId
WHERE A.score>B.score

#查詢" 01 "課程比" 02 "課程成績(jī)高的學(xué)生的信息及課程分?jǐn)?shù)
SELECT * FROM 
`student` 
RIGHT JOIN 
(
SELECT A.SId,A.score class01,B.score class02
FROM (SELECT * FROM SC
WHERE CId='01') A
JOIN
(SELECT * FROM SC
WHERE CId='02') B
ON A.SId=B.SId
WHERE A.score>B.score
) C
ON `student`.`SId`=C.`SId`

1.1 查詢同時(shí)存在" 01 "課程和" 02 "課程的情況

#查詢01課程的情況
SELECT * FROM SC
WHERE CId='01';
#查詢02課程的情況
SELECT * FROM SC
WHERE CId='02'
 #查詢同時(shí)存在" 01 "課程和" 02 "課程的情況
SELECT * FROM 
 (SELECT * FROM SC
WHERE CId='01') a,
(SELECT * FROM SC
WHERE CId='02') b
WHERE a.`SId`=b.SId
#整理
SELECT a.SId,a.CId CId01,a.score score01,b.CId CId02,b.score score02
FROM (SELECT * FROM SC
WHERE CId='01') a,
(SELECT * FROM SC
WHERE CId='02') b
WHERE a.`SId`=b.SId

1.2 查詢存在" 01 "課程但可能不存在" 02 "課程的情況(不存在時(shí)顯示為 null )

 #存在" 01 "課程情況
 SELECT * FROM `sc`
 WHERE `CId`='01'
 
 #存在" 02 "課程情況
 SELECT * FROM sc
 WHERE CId='02'
 
 #查詢存在" 01 "課程但可能不存在" 02 "課程的情況
 SELECT * FROM 
 (SELECT * FROM `sc`
 WHERE `CId`='01') a
LEFT JOIN
( SELECT * FROM sc
 WHERE CId='02') b
 ON a.`SId`=b.SId

1.3 查詢不存在" 01 "課程但存在" 02 "課程的情況

#查詢" 01 "課程的學(xué)生編號(hào)
SELECT `SId` FROM 
SC
WHERE `CId`=01
#查詢" 02 "課程的學(xué)生編號(hào)
SELECT `SId` FROM 
SC
WHERE `CId`=02

SELECT * FROM sc
WHERE SId NOT IN ( SELECT `SId` FROM 
SC
WHERE `CId`=01)
AND `CId`=02

2.查詢平均成績(jī)大于等于 60 分的同學(xué)的學(xué)生編號(hào)和學(xué)生姓名和平均成績(jī)

#查詢平均成績(jī)大于等于 60 分的同學(xué)的學(xué)生編號(hào)和平均成績(jī)
SELECT SId,AVG(`score`)
FROM `sc`
GROUP BY SId
HAVING AVG(`score`)>=60
#兩表聯(lián)合，查詢平均成績(jī)大于等于 60 分的同學(xué)的學(xué)生編號(hào)和學(xué)生姓名和平均成績(jī)
SELECT Student.`Sname`,a.SId,a.平均成績(jī)
FROM `student`
RIGHT JOIN (SELECT `sc`.SId,AVG(`sc`.`score`) 平均成績(jī)
FROM `sc`
GROUP BY SId
HAVING AVG(`score`)>=60) a
ON `student`.`SId`=a.`SId`

3.查詢?cè)?SC 表存在成績(jī)的學(xué)生信息

SELECT DISTINCT student.*
FROM student ,sc
WHERE student.SId=sc.SId

4.查詢所有同學(xué)的學(xué)生編號(hào)、學(xué)生姓名、選課總數(shù)、所有課程的總成績(jī)(沒(méi)成績(jī)的顯示為 null )

#查詢所有同學(xué)的學(xué)生編號(hào)、選課總數(shù)、所有課程的總成績(jī)
SELECT SId,COUNT(CId) 選課總數(shù),SUM(score) 所有課程的總成績(jī)
FROM SC
GROUP BY SId

SELECT Student.`SId`,Student.`Sname`,a.選課總數(shù),a.所有課程的總成績(jī)
FROM Student
LEFT JOIN (SELECT SId,COUNT(CId) 選課總數(shù),SUM(score) 所有課程的總成績(jī)
FROM SC
GROUP BY SId
) a
ON Student.`SId`=a.SId

4.1 查有成績(jī)的學(xué)生信息

SELECT DISTINCT `students`.*
FROM `students`
LEFT JOIN  SC
ON  SC.`SId`=Students.`SId`
WHERE score IS NOT NULL

或

SELECT *
FROM students
WHERE EXISTS(SELECT * FROM sc WHERE students.SId=sc.SId)

5.查詢「李」姓老師的數(shù)量

SELECT COUNT(*)
FROM Teacher
WHERE Teacher.Tname LIKE '李%'

6.查詢學(xué)過(guò)「張三」老師授課的同學(xué)的信息

SELECT Student.* FROM
Teacher ,Course,SC,Student
WHERE Teacher.`TId`=Course.`TId`
AND Course.`CId`=SC.`CId`
AND SC.`SId`=Student.`SId`
AND Teacher.`Tname`='張三'

*7.查詢沒(méi)有學(xué)全所有課程的同學(xué)的信息

SELECT DISTINCT student.*
FROM 
(SELECT student.`SId` ,course.`CId`
FROM `student`,Course) a
LEFT JOIN (SELECT SC.`SId`,sc.`CId`
FROM sc) b
ON a.`SId`=b.`SId`
AND a.`CId`=b.`CId`,student
WHERE b.SId IS NULL
AND   a.SId=student.SId

*8.查詢至少有一門(mén)課與學(xué)號(hào)為" 01 "的同學(xué)所學(xué)相同的同學(xué)的信息

SELECT DISTINCT student.*
FROM sc,student
WHERE cid IN (SELECT SC.CId FROM SC
WHERE SC.`SId`='01')
AND sc.SId=student.`SId`

*9.查詢和" 01 "號(hào)的同學(xué)學(xué)習(xí)的課程 完全相同的其他同學(xué)的信息

SELECT DISTINCT Student.*
FROM (SELECT Student.`SId`,a.cid
FROM Student,(SELECT SC.CId FROM SC
WHERE SC.`SId`='01')a) b LEFT JOIN SC
ON b.`SId`=SC.`SId`
AND b.cid=sc.`CId`,student
WHERE sc.cid IS NULL 
AND b.SId=student.SId

10.查詢沒(méi)學(xué)過(guò)"張三"老師講授的任一門(mén)課程的學(xué)生姓名

SELECT Student.* FROM Student
WHERE Student.`SId` NOT IN (SELECT SC.`SId` FROM 
SC,(SELECT Course.`CId` FROM 
Course,(SELECT Teacher.`TId` FROM  Teacher
WHERE Teacher.`Tname`='張三') a
WHERE Course.`TId`=a.`TId`) b
WHERE SC.`CId`=b.`CId`)

*11.查詢兩門(mén)及其以上不及格課程的同學(xué)的學(xué)號(hào)，姓名及其平均成績(jī)

SELECT Student.`SId`,Student.`Sname`,AVG(SC.`score`)
FROM Student,SC
WHERE Student.`SId`=sc.`SId`
AND   sc.score<60
GROUP BY sc.SId
HAVING COUNT(*)>=2

12.檢索" 01 "課程分?jǐn)?shù)小于 60，按分?jǐn)?shù)降序排列的學(xué)生信息

SELECT Student.*,A.SCORE FROM Student,
(SELECT SC.* FROM SC
WHERE CId='01'
AND score<60) A
WHERE Student.`SId`=A.`SId`
ORDER BY  A.SCORE DESC

13.按平均成績(jī)從高到低顯示所有學(xué)生的所有課程的成績(jī)以及平均成績(jī)

SELECT SC.`SId`,SC.`CId`,SC.`score`,B.a
FROM SC,(SELECT SC.`SId`,AVG(SC.`score`) a
FROM sc
GROUP BY SC.`SId`) B
WHERE SC.`SId`=B.`SId`
ORDER BY a DESC

14.查詢各科成績(jī)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(yōu)良率，優(yōu)秀率 及格為>=60，中等為：70-80，優(yōu)良為：80-90，優(yōu)秀為：>=90 要求輸出課程號(hào)和選修人數(shù)，查詢結(jié)果按人數(shù)降序排列，若人數(shù)相同，按課程號(hào)升序排列

SELECT sc.CId ,Course.`Cname`,MAX(sc.score)AS 最高分,MIN(sc.score)AS 最低分,AVG(sc.score)AS 平均分,
COUNT(*)AS 選修人數(shù),
SUM(CASE WHEN sc.score>=60 THEN 1 ELSE 0 END )/COUNT(*)AS 及格率,
SUM(CASE WHEN sc.score>=70 AND sc.score<80 THEN 1 ELSE 0 END )/COUNT(*)AS 中等率,
SUM(CASE WHEN sc.score>=80 AND sc.score<90  THEN 1 ELSE 0 END )/COUNT(*)AS 優(yōu)良率,
SUM(CASE WHEN sc.score>=90 THEN 1 ELSE 0 END )/COUNT(*)AS 優(yōu)秀率 
FROM sc LEFT JOIN Course
ON sc.`CId`=course.`CId`
GROUP BY sc.CId
ORDER BY COUNT(*)DESC,sc.CId ASC

*15.按各科成績(jī)進(jìn)行排序，并顯示排名， Score 重復(fù)時(shí)保留名次空缺

SELECT sc.CId ,@curRank:=@curRank+1 AS rank,sc.score
FROM (SELECT @curRank:=0) AS t ,sc
ORDER BY sc.score DESC

*15.1 按各科成績(jī)進(jìn)行排序，并顯示排名， Score 重復(fù)時(shí)合并名次

SELECT sc.`CId`,sc.`score`,
CASE WHEN @fontscore=score THEN @curRank
WHEN @fontscore:=score THEN @curRank:=@curRank+1
END AS rank
FROM (SELECT @fontscore := NULL,@curRank:=0) t,sc
ORDER BY sc.score DESC

*16.查詢學(xué)生的總成績(jī)，并進(jìn)行排名，總分重復(fù)時(shí)保留名次空缺

SELECT a.*,
@curRank:=@curRank+1 AS rank
FROM (SELECT  sc.sid,SUM(score) AS scos
FROM sc
GROUP BY sc.sid
ORDER BY scos DESC) a,
(SELECT @curRank:=0) t

*16.1 查詢學(xué)生的總成績(jī)，并進(jìn)行排名，總分重復(fù)時(shí)不保留名次空缺

SELECT a.*,
CASE WHEN @fontscore=a.scos THEN @curRank
WHEN @fontscore:=a.scos THEN @curRank:=@curRank+1
END AS rank
FROM (SELECT  sc.sid,SUM(score) AS scos
FROM sc
GROUP BY sc.sid
ORDER BY scos DESC) a,
(SELECT @sco=NULL ,@curRank:=0) t

*17.統(tǒng)計(jì)各科成績(jī)各分?jǐn)?shù)段人數(shù)：課程編號(hào)，課程名稱(chēng)，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比

SELECT Course.`Cname`,a.*
FROM (SELECT  SC.CId,
CONCAT(SUM(CASE WHEN score>=85 THEN 1 ELSE 0 END)/COUNT(*)*100,"%") AS '[85-100]',
CONCAT(SUM(CASE WHEN sc.score>=70 AND sc.score<85 THEN 1 ELSE 0 END)/COUNT(*)*100,"%") AS '[70-85]',
CONCAT(SUM(CASE WHEN score>=60 AND sc.score<70 THEN 1 ELSE 0 END)/COUNT(*)*100,"%") AS '[60-70]',
CONCAT(SUM(CASE WHEN score<60 THEN 1 ELSE 0 END)/COUNT(*)*100,"%") AS '[0-60]' 
FROM sc
GROUP BY sc.CId) a LEFT JOIN Course
ON a.CId=Course.`CId`

*18.查詢各科成績(jī)前三名的記錄

SELECT * FROM sc
WHERE (SELECT COUNT(*) FROM sc a 
WHERE sc.`CId`=a.`CId` AND sc.score<a.score)<3
ORDER BY CId ASC,sc.score DESC

19.查詢每門(mén)課程被選修的學(xué)生數(shù)

select sc.CId,count(*)
from sc 
GROUP BY sc.CId

*20.查詢出只選修兩門(mén)課程的學(xué)生學(xué)號(hào)和姓名

SELECT SC.SId,Student.`Sname`
FROM SC LEFT JOIN Student
ON SC.`SId`=Student.`SId`
GROUP BY SC.`SId`
HAVING COUNT(*)=2

21.查詢男生、女生人數(shù)

SELECT student.Ssex ,COUNT(*) AS 人數(shù)
FROM student 
GROUP BY student.Ssex

22.查詢名字中含有「風(fēng)」字的學(xué)生信息

SELECT student.* FROM student
WHERE Student.`Sname` LIKE "%風(fēng)%"

*23.查詢同名同性學(xué)生名單，并統(tǒng)計(jì)同名人數(shù)

SELECT *
FROM student LEFT JOIN (SELECT Sname,Ssex,COUNT(*)同名人數(shù) FROM Student GROUP BY Sname,Ssex) AS t1
ON student.Sname =t1.Sname AND student.Ssex=t1.Ssex
WHERE t1.同名人數(shù)>1

*24.查詢 1990 年出生的學(xué)生名單

SELECT * FROM student 
WHERE YEAR(student.`Sage`)=1990

25.查詢每門(mén)課程的平均成績(jī)，結(jié)果按平均成績(jī)降序排列，平均成績(jī)相同時(shí)，按課程編號(hào)升序排列

SELECT SC.`CId`,AVG(SC.`score`) AS 平均成績(jī) FROM sc
GROUP BY SC.`CId` 
ORDER BY 平均成績(jī) DESC,SC.`CId`

26.查詢平均成績(jī)大于等于 85 的所有學(xué)生的學(xué)號(hào)、姓名和平均成績(jī)

SELECT student.SId,student.Sname,t1.平均成績(jī) 
FROM student,(SELECT  SC.SId,AVG(SC.`score`) 平均成績(jī) FROM sc
GROUP BY SC.`SId`
HAVING 平均成績(jī)>=85) t1
WHERE student.`SId`=t1.`SId`

27.查詢課程名稱(chēng)為「數(shù)學(xué)」，且分?jǐn)?shù)低于 60 的學(xué)生姓名和分?jǐn)?shù)

SELECT Student.`Sname`,t.`score`
FROM Student,(SELECT  SC.`SId`,SC.`score` FROM SC
WHERE SC.`CId` IN (SELECT Course.`CId` FROM Course
WHERE Course.`Cname`='數(shù)學(xué)')
AND SC.`score`<60)t
WHERE Student.`SId`=t.`SId`

28.查詢所有學(xué)生的課程及分?jǐn)?shù)情況（存在學(xué)生沒(méi)成績(jī)，沒(méi)選課的情況）

SELECT student.sid,SC.`CId`,sc.`score`
FROM student LEFT JOIN SC
ON student.`SId`=sc.`SId`

29.查詢?nèi)魏我婚T(mén)課程成績(jī)?cè)?70 分以上的姓名、課程名稱(chēng)和分?jǐn)?shù)

SELECT Student.`Sname`,Course.`Cname`,SC.`score`
FROM Student,SC,Course
WHERE Student.`SId`=SC.`SId`
AND SC.`CId`=course.`CId`
AND SC.`score`>=70

30.查詢不及格的課程

SELECT DISTINCT SC.`CId`
FROM SC
WHERE SC.`score`<60

31.查詢課程編號(hào)為 01 且課程成績(jī)?cè)?80 分以上的學(xué)生的學(xué)號(hào)和姓名

SELECT Student.`SId`,Student.`Sname`
FROM Student,SC
WHERE Student.`SId`=sc.`SId`
AND SC.`CId`='01'
AND SC.`score`>80

32.求每門(mén)課程的學(xué)生人數(shù)

SELECT SC.`CId`,COUNT(*) 學(xué)生人數(shù)
FROM SC
GROUP BY SC.`CId`

*33.成績(jī)不重復(fù)，查詢選修「張三」老師所授課程的學(xué)生中，成績(jī)最高的學(xué)生信息及其成績(jī)

select student.*,sc.score
from student ,course ,teacher ,sc
where course.CId=sc.CId
and course.TId=teacher.TId
and teacher.Tname='張三'
and student.SId =sc.SId
LIMIT 1

*34.成績(jī)有重復(fù)的情況下，查詢選修「張三」老師所授課程的學(xué)生中，成績(jī)最高的學(xué)生信息及其成績(jī)

SELECT Student.*,c.score
FROM Student,(SELECT a.SId,a.score, 
CASE WHEN @fontage=a.score THEN @rank 
WHEN @fontage:=a.score THEN @rank:=@rank+1 END  AS rank
FROM 
(SELECT Sc.SId,SC.`score`  
FROM sc,course ,teacher 
WHERE sc.CId=course.CId
AND course.TId=teacher.TId
AND teacher.Tname='張三'
ORDER BY sc.score DESC) a,(SELECT @fontage:=NULL,@rank:=0) b) c
WHERE Student.`SId`=c.SId
AND c.rank=1

*35.查詢不同課程成績(jī)相同的學(xué)生的學(xué)生編號(hào)、課程編號(hào)、學(xué)生成績(jī)

SELECT DISTINCT a.sid,a.cid,a.score FROM sc a LEFT JOIN sc b
ON a.SId=b.SId
WHERE a.cid!=b.cid
AND a.score=b.score

*36.查詢每門(mén)功成績(jī)最好的前兩名

SELECT * FROM sc a
WHERE
(SELECT COUNT(*) FROM sc b
WHERE a.CId=b.CId
AND b.score>a.score)<2
ORDER BY a.cid

37.統(tǒng)計(jì)每門(mén)課程的學(xué)生選修人數(shù)（超過(guò) 5 人的課程才統(tǒng)計(jì)）

SELECT SC.`CId`,COUNT(*)
FROM sc
GROUP BY SC.`CId`
HAVING COUNT(*)>5

*38.檢索至少選修兩門(mén)課程的學(xué)生學(xué)號(hào)

SELECT sc.`SId`,COUNT(*) FROM sc
GROUP BY sc.`SId`
HAVING COUNT(*)>=2

39.查詢選修了全部課程的學(xué)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.查詢各學(xué)生的年齡，只按年份來(lái)算

select *, year(now())-year(sage) as age from student;

*41.按照出生日期來(lái)算，當(dāng)前月日 < 出生年月的月日則，年齡減一

SELECT *,TIMESTAMPDIFF(YEAR,sage,NOW())AS 學(xué)生年齡 
FROM student

*42.查詢本周過(guò)生日的學(xué)生

SELECT *, SUBSTR(YEARWEEK(student.Sage),5,2) AS birth_week, 
SUBSTR(YEARWEEK(CURDATE()),5,2) AS now_week 
FROM student 
HAVING SUBSTR(YEARWEEK(student.Sage),5,2)=SUBSTR(YEARWEEK(CURDATE()),5,2);

*43.查詢下周過(guò)生日的學(xué)生

select     *,    substr(YEARWEEK(student.Sage),5,2) as birth_week,    substr(YEARWEEK(CURDATE()),5,2) as now_week from student having substr(YEARWEEK(student.Sage),5,2)=        substr(YEARWEEK(CURDATE()),5,2)+1;

*44.查詢本月過(guò)生日的學(xué)生

select *, month(sage) as birth_month, month(now()) as now_month from student where month(sage)=month(now());

*45.查詢下月過(guò)生日的學(xué)生

select *, month(sage) as birth_month, month(now()) as now_month from student where month(sage)=month(now())+1
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