Mysql练习45题

1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数

SELECT st.*,sc.s_score AS '语文' ,sc2.s_score AS '数学' 
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id AND sc.c_id='01' 
LEFT JOIN score sc2 ON sc2.s_id=st.s_id AND sc2.c_id='02'  
WHERE sc.s_score>sc2.s_score

2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数SELECT

st.*,sc.s_score AS '语文' ,sc2.s_score '数学' 
SELECT st.*,sc.s_score AS '语文' ,sc2.s_score AS '数学' 
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id AND sc.c_id='01' 
LEFT JOIN score sc2 ON sc2.s_id=st.s_id AND sc2.c_id='02'  
WHERE sc.s_score<sc2.s_score

3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩

SELECT st.s_id,st.s_name,AVG(sc.s_score) AS '平均成绩'
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id HAVING AVG(sc.s_score)>=60

4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩

    -- (包括有成绩的和无成绩的)

SELECT st.s_id,st.s_name,IFNULL(AVG(sc.s_score),0) AS '平均成绩'
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id HAVING AVG(sc.s_score)<60 OR AVG(sc.s_score) IS NULL

5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

SELECT st.s_id,st.s_name,COUNT(c.c_id) AS '选课总数',IFNULL(SUM(sc.s_score),0) AS '总成绩'
FROM student st
LEFT JOIN score sc ON sc.s_id =st.s_id 
LEFT JOIN course c ON c.c_id=sc.c_id
GROUP BY st.s_id

6、查询"李"姓老师的数量

SELECT t.t_name,COUNT(t.t_id) AS '数量' FROM teacher t
GROUP BY t.t_id HAVING t.t_name LIKE "李%"; 

7、查询学过"张三"老师授课的同学的信息

SELECT st.*
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
LEFT JOIN course c ON c.c_id=sc.c_id
LEFT JOIN teacher t ON t.t_id=c.t_id
WHERE t.t_name="张三"

8、查询没学过"张三"老师授课的同学的信息

SELECT st.* 
 FROM student st 
 WHERE st.s_id NOT IN(
  SELECT sc.s_id FROM score sc 
	LEFT JOIN course c ON c.c_id=sc.c_id
	LEFT JOIN teacher t ON t.t_id=c.t_id
	WHERE t.t_name="张三"
  )

9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

SELECT st.*
FROM student st
INNER JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id
HAVING SUM(IF(sc.c_id="01" OR sc.c_id="02" ,1,0))>1

10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

SELECT st.* 
FROM student st 
INNER JOIN score sc ON sc.s_id = st.s_id
INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id="01"
WHERE st.s_id NOT IN (
SELECT st2.s_id FROM student st2 
INNER JOIN score sc2 ON sc2.s_id = st2.s_id
INNER JOIN course c2 ON c2.c_id=sc2.c_id AND c2.c_id="02"
)

11、查询没有学全所有课程的同学的信息

SELECT st.* FROM Student st
LEFT JOIN score sc ON st.s_id = sc.s_id
GROUP BY st.s_id HAVING COUNT(c_id)<(SELECT COUNT(c_id) FROM Course)

12、查询至少有一门课与学号为"01"的同学所学相同的同学的信息

SELECT DISTINCT st.* 
FROM student st 
LEFT JOIN score sc ON sc.s_id=st.s_id
WHERE sc.c_id IN (
SELECT sc2.c_id FROM student st2
LEFT JOIN score sc2 ON sc2.s_id=st2.s_id
WHERE st2.s_id ='01'
)

13、查询和"01"号的同学学习的课程完全相同的其他同学的信息

SELECT  st.* 
FROM student st 
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id HAVING GROUP_CONCAT(sc.c_id) = 
(
SELECT  GROUP_CONCAT(sc2.c_id) FROM student st2
LEFT JOIN score sc2 ON sc2.s_id=st2.s_id
WHERE st2.s_id ='01'
)

14、查询没学过"张三"老师讲授的任一门课程的学生姓名

 SELECT st.s_name
 FROM student st 
 WHERE st.s_id NOT IN(
  SELECT sc.s_id FROM score sc 
	LEFT JOIN course c ON c.c_id=sc.c_id
	LEFT JOIN teacher t ON t.t_id=c.t_id
	WHERE t.t_name="张三"
  )

15、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

SELECT st.s_id,st.s_name,AVG(sc.s_score) 
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
WHERE sc.s_id IN (
SELECT sc.s_id FROM score sc 
WHERE sc.s_score<60 OR sc.s_score IS NULL
GROUP BY sc.s_id HAVING COUNT(sc.s_id)>=2
)
GROUP BY st.s_id

16、检索"01"课程分数小于60，按分数降序排列的学生信息

SELECT st.*,sc.s_score 
FROM student st 
INNER JOIN score sc ON sc.s_id=st.s_id AND sc.c_id="01" AND sc.s_score<60
ORDER BY sc.s_score DESC

17、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

SELECT st.s_id,st.s_name,IFNULL(AVG(sc4.s_score),0) AS "平均分",IFNULL(sc.s_score,0) AS "语文",IFNULL(sc2.s_score,0) AS "数学",IFNULL(sc3.s_score,0) AS "英语" 
FROM student st
LEFT JOIN score sc  ON sc.s_id=st.s_id  AND sc.c_id="01"
LEFT JOIN score sc2 ON sc2.s_id=st.s_id AND sc2.c_id="02"
LEFT JOIN score sc3 ON sc3.s_id=st.s_id AND sc3.c_id="03"
LEFT JOIN score sc4 ON sc4.s_id=st.s_id
GROUP BY st.s_id 
ORDER BY SUM(sc4.s_score) DESC

18.查询各科成绩最高分、最低分和平均分：以如下形式显示：课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率

------ 及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90

SELECT sc.c_id,co.c_name,MAX(sc.s_score)"最高分",MIN( sc.s_score)"最低分",AVG(sc.s_score)"平均分",
(SUM(IF(sc.s_score>=60,1,0))/COUNT(1))"及格率",(SUM(IF(sc.s_score>=70 AND sc.s_score<80,1,0))/COUNT(1))"中等率",
(SUM(IF(sc.s_score>=80 AND sc.s_score<90,1,0))/COUNT(1))"优良率",(SUM(IF(sc.s_score>=90,1,0))/COUNT(1))"优秀率"
FROM score sc
INNER JOIN course co ON co.c_id = sc.c_id
GROUP BY sc.c_id

19、按各科成绩进行排序，并显示排名(实现不完全)

SELECT s_id,a.c_id,c_name,s_score,rank FROM (
SELECT s_id,c_id,s_score,
CASE 
	WHEN c_id = @cid THEN 
		IF(@prevRank = s_score,@curRank,@curRank := @curRank + 1)
	ELSE 
		@curRank := 1
END AS rank,
@cid := c_id,
@prevRank := s_score
FROM score, (SELECT @cid:=NULL,@prevRank:=NULL,@curRank:=0) p
ORDER BY c_id,s_score DESC) a LEFT JOIN course ON a.c_id=course.c_id

20、查询学生的总成绩并进行排名

SELECT st.s_id,st.s_name,(CASE WHEN SUM(sc.s_score) IS NULL THEN 0 ELSE SUM(sc.s_score) END)
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id ORDER BY SUM(sc.s_score) DESC

21、查询不同老师所教不同课程平均分从高到低显示

SELECT t.t_id,t.t_name,c.c_name,AVG(sc.s_score) FROM teacher t 
LEFT JOIN course c ON c.t_id=t.t_id 
LEFT JOIN score sc ON sc.c_id =c.c_id
GROUP BY t.t_id
ORDER BY AVG(sc.s_score) DESC 

22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

SELECT a.* FROM (
SELECT st.*,c.c_id,c.c_name,sc.s_score FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id =sc.c_id AND c.c_id="01"
ORDER BY sc.s_score DESC LIMIT 1,2 ) a
UNION ALL
SELECT b.* FROM (
SELECT st.*,c.c_id,c.c_name,sc.s_score FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id =sc.c_id AND c.c_id="02"
ORDER BY sc.s_score DESC LIMIT 1,2) b
UNION ALL
SELECT c.* FROM (
SELECT st.*,c.c_id,c.c_name,sc.s_score FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id =sc.c_id AND c.c_id="03"
ORDER BY sc.s_score DESC LIMIT 1,2) c

23、统计各科成绩各分数段人数：课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]及所占百分比

SELECT c.c_id,c.c_name 
,((SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id AND sc.s_score<=100 AND sc.s_score>80)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id )) "100-85"
,((SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id AND sc.s_score<=85 AND sc.s_score>70)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id )) "85-70"
,((SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id AND sc.s_score<=70 AND sc.s_score>60)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id )) "70-60"
,((SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id AND sc.s_score<=60 AND sc.s_score>=0)/(SELECT COUNT(1) FROM score sc WHERE sc.c_id=c.c_id )) "60-0"
FROM course c ORDER BY c.c_id

24、查询学生平均成绩及其名次

SET @i=0;
SELECT a.*,@i:=@i+1 FROM (
SELECT st.s_id,st.s_name,ROUND((CASE WHEN AVG(sc.s_score) IS NULL THEN 0 ELSE AVG(sc.s_score) END),2) "平均分" FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id ORDER BY sc.s_score DESC) a

25、查询各科成绩前三名的记录

SELECT a.* FROM (
 SELECT st.s_id,st.s_name,c.c_id,c.c_name,sc.s_score FROM student st
 LEFT JOIN score sc ON sc.s_id=st.s_id
 INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id='01'
 ORDER BY sc.s_score DESC LIMIT 0,3) a
UNION ALL 
SELECT b.* FROM (
 SELECT st.s_id,st.s_name,c.c_id,c.c_name,sc.s_score FROM student st
 LEFT JOIN score sc ON sc.s_id=st.s_id
 INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id='02'
 ORDER BY sc.s_score DESC LIMIT 0,3) b
UNION ALL
SELECT c.* FROM (
 SELECT st.s_id,st.s_name,c.c_id,c.c_name,sc.s_score FROM student st
 LEFT JOIN score sc ON sc.s_id=st.s_id
 INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id='03'
 ORDER BY sc.s_score DESC LIMIT 0,3) c

26、查询每门课程被选修的学生数

SELECT c.c_id,c.c_name,COUNT(1) 
FROM course c 
LEFT JOIN score sc ON sc.c_id=c.c_id
INNER JOIN student st ON st.s_id=c.c_id
GROUP BY st.s_id

27、查询出只有两门课程的全部学生的学号和姓名

SELECT st.s_id,st.s_name 
FROM student st 
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id=sc.c_id 
GROUP BY st.s_id HAVING COUNT(1)=2

28、查询男生、女生人数

SELECT st.s_sex,COUNT(1) 
FROM student st 
GROUP BY st.s_sex

29、查询名字中含有"风"字的学生信息

SELECT st.* 
FROM student st
WHERE st.s_name LIKE "%风%";

30、查询同名同性学生名单，并统计同名人数

SELECT st.*,COUNT(1)
FROM student st
GROUP BY st.s_name,st.s_sex HAVING COUNT(1)>1

31、查询1990年出生的学生名单

SELECT st.*
FROM student st 
WHERE st.s_birth LIKE "1990%"

32、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

SELECT c.c_id,c.c_name,AVG(sc.s_score) 
FROM course c
INNER JOIN score sc ON sc.c_id=c.c_id  
GROUP BY c.c_id ORDER BY AVG(sc.s_score) DESC,c.c_id ASC

33、查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩

SELECT st.s_id,st.s_name,AVG(sc.s_score) 
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id HAVING AVG(sc.s_score)>=85

34、查询课程名称为"数学"，且分数低于60的学生姓名和分数

SELECT st.s_id,st.s_name,sc.s_score
FROM student st
INNER JOIN score sc ON sc.s_id=st.s_id AND sc.s_score<60
INNER JOIN course c ON c.c_id=sc.c_id AND c.c_name ="数学" 

35、查询所有学生的课程及分数情况；

SELECT st.s_id,st.s_name,c.c_name,sc.s_score 
FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
LEFT JOIN course c ON c.c_id =sc.c_id
ORDER BY st.s_id,c.c_name

36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数

SELECT st2.s_id,st2.s_name,c2.c_name,sc2.s_score 
FROM student st2
LEFT JOIN score sc2 ON sc2.s_id=st2.s_id
LEFT JOIN course c2 ON c2.c_id=sc2.c_id 
WHERE st2.s_id IN(
SELECT st.s_id FROM student st 
GROUP BY st.s_id HAVING sc2.s_score>=70)
ORDER BY s_id

SELECT st.s_id,st.s_name,c.c_name,sc.s_score 
FROM student st
INNER JOIN score sc ON sc.s_id=st.s_id AND sc.s_score>=70
INNER JOIN course c ON c.c_id=sc.c_id

37、查询不及格的课程

SELECT st.s_id,c.c_name,st.s_name,sc.s_score 
FROM student st
INNER JOIN score sc ON sc.s_id=st.s_id AND  sc.s_score<60
INNER JOIN course c ON c.c_id=sc.c_id

38、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名

SELECT st.s_id,st.s_name,sc.s_score 
FROM student st
INNER JOIN score sc ON sc.s_id=st.s_id AND sc.c_id="01" AND sc.s_score>=80

39、求每门课程的学生人数

SELECT c.c_id,c.c_name,COUNT(1) 
FROM course c
INNER JOIN score sc ON sc.c_id=c.c_id
GROUP BY c.c_id

40、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩

SELECT st.*,c.c_name,sc.s_score,t.t_name FROM student st
INNER JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id=sc.c_id 
INNER JOIN teacher t ON t.t_id=c.t_id AND  t.t_name="张三"
ORDER BY sc.s_score DESC
LIMIT 0,1

41、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

SELECT st.s_id,st.s_name,sc.c_id,sc.s_score 
FROM student st 
LEFT JOIN score sc ON sc.s_id=st.s_id
LEFT JOIN course c ON c.c_id=sc.c_id
WHERE (
SELECT COUNT(1) FROM student st2 
LEFT JOIN score sc2 ON sc2.s_id=st2.s_id
LEFT JOIN course c2 ON c2.c_id=sc2.c_id
WHERE sc.s_score=sc2.s_score AND c.c_id!=c2.c_id 
)>1

42、查询每门功成绩最好的前两名

SELECT a.* FROM (SELECT st.s_id,st.s_name,c.c_name,sc.s_score FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id="01"
ORDER BY sc.s_score DESC LIMIT 0,2) a
UNION ALL
SELECT b.* FROM (SELECT st.s_id,st.s_name,c.c_name,sc.s_score FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id="02"
ORDER BY sc.s_score DESC LIMIT 0,2) b
UNION ALL
SELECT c.* FROM (SELECT st.s_id,st.s_name,c.c_name,sc.s_score FROM student st
LEFT JOIN score sc ON sc.s_id=st.s_id
INNER JOIN course c ON c.c_id=sc.c_id AND c.c_id="03"
ORDER BY sc.s_score DESC LIMIT 0,2) c

 SELECT a.s_id,a.c_id,a.s_score 
 FROM score a
 WHERE (SELECT COUNT(1) FROM score b WHERE b.c_id=a.c_id AND b.s_score>=a.s_score)<=2 ORDER BY a.c_id

– 43、统计每门课程的学生选修人数（超过5人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，
– 若人数相同，按课程号升序排列

SELECT sc.c_id,COUNT(1)
FROM score sc
LEFT JOIN course c ON c.c_id=sc.c_id
GROUP BY c.c_id HAVING COUNT(1)>5
ORDER BY COUNT(1) DESC,sc.c_id ASC

44、检索至少选修两门课程的学生学号

SELECT st.s_id 
FROM student st 
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id HAVING COUNT(1)>=2

45、查询选修了全部课程的学生信息

SELECT st.* 
FROM student st 
LEFT JOIN score sc ON sc.s_id=st.s_id
GROUP BY st.s_id HAVING COUNT(1)=(SELECT COUNT(1) FROM course)