MySQL練習-主外鍵多表查詢

練習:

1.建立表關系:

請創建如下表，並創建相關約束

 

USE db1;
CREATE TABLE class(
    cid INT AUTO_INCREMENT PRIMARY KEY,
    caption VARCHAR(10)
);
CREATE TABLE teacher(
    tid INT AUTO_INCREMENT PRIMARY KEY,
    tname VARCHAR(10)
);
CREATE TABLE course(
    cid INT AUTO_INCREMENT PRIMARY KEY,
    cname VARCHAR(10),
    teach_id INT,
    CONSTRAINT fk_course_teacher FOREIGN KEY(teach_id) REFERENCES teacher(tid)
);
CREATE TABLE student(
    sid INT AUTO_INCREMENT PRIMARY KEY,
    sname VARCHAR(10),
    gender VARCHAR(10),
    class_id INT,
    CONSTRAINT fk_student_class FOREIGN KEY(class_id) REFERENCES class(cid)
);
CREATE TABLE score(
    sid INT AUTO_INCREMENT PRIMARY KEY,
    student_id INT,
    course_id INT,
    number INT,
    CONSTRAINT fk_score_student FOREIGN KEY(student_id) REFERENCES student(sid),
    CONSTRAINT fk_score_course FOREIGN KEY(course_id) REFERENCES course(cid)
);

INSERT INTO class(caption) VALUES("三年二班");
INSERT INTO class(caption) VALUES("一年三班");
INSERT INTO class(caption) VALUES("三年一班");

INSERT INTO teacher(tname) VALUES("波多");
INSERT INTO teacher(tname) VALUES("蒼空");
INSERT INTO teacher(tname) VALUES("飯島");

INSERT INTO student(sname,gender,class_id) VALUES("鋼蛋","女",1);
INSERT INTO student(sname,gender,class_id) VALUES("鐵錘","女",1);
INSERT INTO student(sname,gender,class_id) VALUES("山炮","男",2);

INSERT INTO course(cname,teach_id) VALUES("生物",1);
INSERT INTO course(cname,teach_id) VALUES("體育",1);
INSERT INTO course(cname,teach_id) VALUES("物理",2);

INSERT INTO score(student_id,course_id,number) VALUES(1,1,60);
INSERT INTO score(student_id,course_id,number) VALUES(1,2,59);
INSERT INTO score(student_id,course_id,number) VALUES(2,2,100);

ALTER TABLE score ADD UNIQUE sco_que(student_id,course_id);

2.操作練習:

1、自行創建測試數據

INSERT INTO student(sname,gender,class_id) VALUES("鋼鐵俠","男",4);
-- Cannot add or update a child row: a foreign key constraint fails (`db1`.`student`, CONSTRAINT `fk_student_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`))

2、查詢“生物”課程比“物理”課程成績高的所有學生的學號；

SELECT s1.student_id FROM (SELECT a.student_id,a.`number` FROM score a,course b 
WHERE a.`course_id` = b.`cid` AND b.`cname` ="生物") s1 , (SELECT a.student_id,a.`number` FROM score a,course b 
WHERE a.`course_id` = b.`cid` AND b.`cname`="體育") s2
WHERE s1.`student_id` = s2.student_id AND s1.number >s2.number

3、查詢平均成績大於60分的同學的學號和平均成績；

SELECT student_id,AVG(number)
FROM score 
GROUP BY student_id
HAVING AVG(number) > 60

4、查詢所有同學的學號、姓名、選課數、總成績；

SELECT a.`sid`,a.`sname`,b.`cname`,c.`number`,c.`course_id`,a.`class_id` 
FROM student a,course b,score c
WHERE a.`sid` = c.`student_id` AND c.`course_id` = b.`cid`

5、查詢姓“李”的老師的個數；

SELECT count(*) as a from teacher where tname LIKE '李%'

6、查詢沒學過“葉平”老師課的同學的學號、姓名；

SELECT a.sid,a.sname FROM student a,teacher b,course c
WHERE a.class_id = c.cid and b.tid = c.teach_id AND b.tname != '葉平'

7、查詢學過“001”並且也學過編號“002”課程的同學的學號、姓名；

SELECT a.`student_id`,c.`sname` FROM score a , score b ,student c
WHERE a.`student_id`=b.`student_id` AND a.`course_id` ='1' 
AND b.`course_id`='2' AND c.`sid` = a.`student_id`

8、查詢學過“葉平”老師所教的所有課的同學的學號、姓名；

SELECT c.`sid`,c.`sname` FROM student c 
LEFT JOIN score d ON c.`sid` = d.`student_id`
LEFT JOIN course b ON d.`course_id` = b.`cid`
LEFT JOIN teacher a ON a.`tid` = b.`teach_id`
WHERE a.`tname`='波多'
GROUP BY c.`sname`
HAVING COUNT(c.sname)
<(SELECT COUNT(*) FROM teacher a 
LEFT JOIN course b ON a.`tid` = b.`teach_id`
WHERE a.`tname`='波多')

9、查詢課程編號“002”的成績比課程編號“001”課程低的所有同學的學號、姓名；

SELECT s1.student_id FROM (SELECT a.student_id,a.`number` FROM score a,course b 
WHERE a.`course_id` = b.`cid` AND b.`cid` ='2') s1 , (SELECT a.student_id,a.`number` FROM score a,course b 
WHERE a.`course_id` = b.`cid` AND b.`cid`='1') s2
WHERE s1.`student_id` = s2.student_id AND s1.number >s2.number

10、查詢有課程成績小於60分的同學的學號、姓名；

SELECT a.`sid`,a.`sname` FROM student a , score    b
WHERE a.sid = b.student_id AND number < 60

11、查詢沒有學全所有課的同學的學號、姓名；

SELECT a.`sid`,a.`sname` FROM student a 
LEFT JOIN score b ON  a.`sid` = b.`student_id`
GROUP BY a.`sid`
HAVING COUNT(b.`student_id`) < (SELECT COUNT(*) FROM course)

12、查詢至少有一門課與學號為“001”的同學所學相同的同學的學號和姓名；

SELECT a.`sid`,a.`sname` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course c ON c.`cid` = b.`course_id`
WHERE c.`cid` IN (
SELECT cc.`cid` FROM student aa LEFT JOIN score bb ON aa.`sid` = bb.`student_id`
LEFT JOIN course cc ON cc.`cid` = bb.`course_id` WHERE aa.`sid`='1'
) AND a.`sid` !='1'

13、查詢至少學過學號為“001”同學所選課程中任意一門課的其他同學學號和姓名；

SELECT a.`sid`,a.`sname` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course c ON c.`cid` = b.`course_id`
WHERE c.`cid` IN (
SELECT cc.`cid` FROM student aa LEFT JOIN score bb ON aa.`sid` = bb.`student_id`
LEFT JOIN course cc ON cc.`cid` = bb.`course_id` WHERE aa.`sid`='1'
) AND a.`sid` !='1'

14、查詢和“002”號的同學學習的課程完全相同的其他同學學號和姓名；

SELECT a.`sid`,a.`sname` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course ac ON b.`course_id`=ac.`cid`
WHERE
 ac.`cid` IN (SELECT c.`cid` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course c ON b.`course_id`=c.`cid` WHERE a.`sid`='2') 
AND a.`sid` != '2' 
GROUP BY a.`sid`,a.`sname`
HAVING
(SELECT COUNT(ac.`cid`) AS countCid FROM student aa LEFT JOIN score b ON aa.`sid` = b.`student_id`
LEFT JOIN course ac ON b.`course_id`=ac.`cid` WHERE aa.`sid`=a.`sid`)
 = (SELECT COUNT(c.`cid`) AS cc FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course c ON b.`course_id`=c.`cid` WHERE a.`sid`='2')

15、刪除學習“葉平”老師課的SC表記錄；

DELETE FROM score WHERE course_id IN (
SELECT a.`cid` FROM course a LEFT JOIN teacher b ON a.`teach_id`=b.`tid`
WHERE b.`tname`='葉平'
)

16、向SC表中插入一些記錄，這些記錄要求符合以下條件：①沒有上過編號“002”課程的同學學號；②插入“002”號課程的平均成績；
17、按平均成績從低到高顯示所有學生的“語文”、“數學”、“英語”三門的課程成績，按如下形式顯示： 學生ID,語文,數學,英語,有效課程數,有效平均分；
18、查詢各科成績最高和最低的分：以如下形式顯示：課程ID，最高分，最低分；
19、按各科平均成績從低到高和及格率的百分數從高到低順序；
20、課程平均分從高到低顯示（現實任課老師）；
21、查詢各科成績前三名的記錄:(不考慮成績並列情況)
22、查詢每門課程被選修的學生數；
23、查詢出只選修了一門課程的全部學生的學號和姓名；
24、查詢男生、女生的人數；
25、查詢姓“張”的學生名單；
26、查詢同名同姓學生名單，並統計同名人數；
27、查詢每門課程的平均成績，結果按平均成績升序排列，平均成績相同時，按課程號降序排列；
28、查詢平均成績大於85的所有學生的學號、姓名和平均成績；
29、查詢課程名稱為“數學”，且分數低於60的學生姓名和分數；
30、查詢課程編號為003且課程成績在80分以上的學生的學號和姓名；
31、求選了課程的學生人數
32、查詢選修“楊艷”老師所授課程的學生中，成績最高的學生姓名及其成績；
33、查詢各個課程及相應的選修人數；
34、查詢不同課程但成績相同的學生的學號、課程號、學生成績；

35、查詢每門課程成績最好的前兩名；

SELECT student_id FROM score 
ORDER BY number DESC LIMIT 2

36、檢索至少選修兩門課程的學生學號；

SELECT a.`sid` FROM student a LEFT JOIN score b ON a.`sid` = b.`student_id`
GROUP BY a.`sid`
HAVING COUNT(a.`sid`)>=2

37、查詢全部學生都選修的課程的課程號和課程名；

SELECT DISTINCT c.`cid`,c.`cname` FROM student a 
LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course c ON b.`course_id`=c.`cid`

38、查詢沒學過“葉平”老師講授的任一門課程的學生姓名；

SELECT a.`sname` FROM student a 
LEFT JOIN score b ON a.`sid` = b.`student_id`
LEFT JOIN course c ON c.`cid` = b.`course_id`
WHERE c.`cid` NOT IN (
SELECT cour.`cid` FROM teacher teac 
LEFT JOIN course cour ON teac.`tid`=cour.`teach_id`
WHERE teac.`tname` = '波多' 
)

39、查詢兩門以上不及格課程的同學的學號及其平均成績；

SELECT student_id,COUNT(sid) AS co,AVG(number)AS avgg  FROM score 
WHERE number < 60 
GROUP BY student_id
HAVING co >=2

40、檢索“004”課程分數小於60，按分數降序排列的同學學號；

SELECT b.`sid`,b.`sname`,a.`number` FROM score a LEFT JOIN student b ON a.`student_id` = b.`sid`
WHERE a.`course_id` = '4' AND a.`number` < '60'
ORDER BY a.`number` DESC

41、刪除“002”同學的“001”課程的成績；

DELETE FROM score WHERE student_id ='2' AND course_id = '1'