MySQL练习-主外键多表查询

练习:

1.建立表关系:

请创建如下表，并创建相关约束

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("苍空");
INSERT INTO teacher(tname) VALUES("饭岛");

INSERT INTO student(sname,gender,class_id) VALUES("钢蛋","女",1);
INSERT INTO student(sname,gender,class_id) VALUES("铁锤","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("体育",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.操作练习:

1、自行创建测试数据

INSERT INTO student(sname,gender,class_id) VALUES("钢铁侠","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、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

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`="体育") s2
WHERE s1.`student_id` = s2.student_id AND s1.number >s2.number

3、查询平均成绩大于60分的同学的学号和平均成绩；

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

4、查询所有同学的学号、姓名、选课数、总成绩；

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、查询姓“李”的老师的个数；

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

6、查询没学过“叶平”老师课的同学的学号、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 != '叶平'

7、查询学过“001”并且也学过编号“002”课程的同学的学号、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、查询学过“叶平”老师所教的所有课的同学的学号、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、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、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、查询有课程成绩小于60分的同学的学号、姓名；

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

11、查询没有学全所有课的同学的学号、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、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名；

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、查询至少学过学号为“001”同学所选课程中任意一门课的其他同学学号和姓名；

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、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名；

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、删除学习“叶平”老师课的SC表记录；

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`='叶平'
)

16、向SC表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“002”课程的同学学号；②插入“002”号课程的平均成绩；
17、按平均成绩从低到高显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分；
19、按各科平均成绩从低到高和及格率的百分数从高到低顺序；
20、课程平均分从高到低显示（现实任课老师）；
21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
22、查询每门课程被选修的学生数；
23、查询出只选修了一门课程的全部学生的学号和姓名；
24、查询男生、女生的人数；
25、查询姓“张”的学生名单；
26、查询同名同姓学生名单，并统计同名人数；
27、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；
28、查询平均成绩大于85的所有学生的学号、姓名和平均成绩；
29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
31、求选了课程的学生人数
32、查询选修“杨艳”老师所授课程的学生中，成绩最高的学生姓名及其成绩；
33、查询各个课程及相应的选修人数；
34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；

35、查询每门课程成绩最好的前两名；

SELECT student_id FROM score 
ORDER BY number DESC LIMIT 2

36、检索至少选修两门课程的学生学号；

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、查询全部学生都选修的课程的课程号和课程名；

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、查询没学过“叶平”老师讲授的任一门课程的学生姓名；

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、查询两门以上不及格课程的同学的学号及其平均成绩；

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

40、检索“004”课程分数小于60，按分数降序排列的同学学号；

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、删除“002”同学的“001”课程的成绩；

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