mysql练习题1

标签：练习题 num course score student mysql id SELECT

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

SELECT C.student_id, C.SHENGWU, D.WULI FROM

( SELECT A.student_id, A.number AS SHENGWU FROM socke A LEFT JOIN corse B ON A.corse_id = B.cid WHERE B.cname = '生物' ) AS C

LEFT JOIN ( SELECT socke.student_id, socke.number AS WULI FROM socke LEFT JOIN corse ON socke.corse_id = corse.cid WHERE corse.cname = '物理' ) AS D

ON C.student_id = D.student_id WHERE shengwu>=wuli #SHENGWU >= IF(ISNULL(WULI),0,WULI)；

查看源码

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 socke GROUP BY student_id HAVING AVG(number)>60 ;
SELECT student_id,AVG(number) as PJ from socke GROUP BY student_id HAVING PJ>60 ORDER BY PJ DESC;

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4、查询所有同学的学号、姓名、选课数、总成绩；

 SELECT socke.student_id,student.sname,COUNT(1),SUM(socke.number) FROM socke LEFT JOIN student on socke.student_id=student.sid GROUP BY socke.student_id;
SELECT socke.student_id,student.sname,COUNT(1),SUM(socke.number) FROM socke LEFT JOIN student on socke.student_id=student.sid GROUP BY socke.student_id ORDER BY SUM(socke.number);

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5、查询姓“李”的老师的个数；

SELECT COUNT(1) from teacher WHERE tname LIKE '李%';

查看源码

 6、查询没学过“李平”老师课的同学的学号、姓名；

SELECT    student_id,    sname FROM socke    LEFT JOIN student ON socke.student_id = student.sid
WHERE    socke.student_id NOT IN (SELECT socke.student_id FROM    socke    WHERE    socke.corse_id IN (
SELECT corse.cid FROM    corse    WHERE    corse.teacher_id IN (
SELECT teacher.tid FROM teacher    WHERE teacher.tname = '李平老师')            )
GROUP BY    socke.student_id)

查看源码

 select * from student where sid not in (
        select DISTINCT student_id from score where score.course_id in (
            select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '李平老师'
        )
    )

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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    student.sname,    score.student_id
FROM    score  LEFT JOIN student ON score.course_id = student.sid
WHERE    score.course_id = 1 OR score.course_id = 2
GROUP BY    score.student_id HAVING     COUNT(1) > 1;

查看源码

8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；

SELECT * FROM score where course_id in
(SELECT cid from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE teacher.tname='李平老师') 
GROUP BY student_id HAVING COUNT(1)=(SELECT COUNT(cid) from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE teacher.tname='李平老师');

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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 a.student_id,a.sname FROM
(SELECT score.sid,score.student_id,score.num,student.sname from score LEFT JOIN student on score.student_id= student.sid WHERE course_id=2)as A LEFT JOIN
(SELECT score.sid,score.student_id,score.num,student.sname from score LEFT JOIN student on score.student_id= student.sid WHERE course_id=1)as B 
on A.student_id=b.student_id WHERE a.num>b.num;

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10、查询有课程成绩小于60分的同学的学号、姓名；

SELECT  DISTINCT(score.student_id),student.sname from score LEFT JOIN student on score.student_id=student.sid  WHERE score.num<60;

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11、查询没有学全所有课的同学的学号、姓名；

SELECT score.student_id,student.sname FROM score LEFT JOIN student on score.student_id=student.sid 
GROUP BY score.student_id HAVING COUNT(1)<(SELECT COUNT(1) from course);

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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 DISTINCT(score.student_id),student.sname from score LEFT JOIN student on score.student_id=student.sid  
where score.course_id in (SELECT score.course_id from score WHERE score.student_id=1) and score.student_id!=1;

查看源码 查看源码

13、查询至少学过学号为“001”同学所有课的其他同学学号和姓名；

SELECT student.sname,    student_id,    COUNT(1) FROM    score LEFT JOIN student on score.student_id= student.sid
WHERE    student_id != 1 AND course_id IN (
SELECT        course_id    FROM        score    WHERE        score.student_id = 1) 
GROUP BY    student_id HAVING    COUNT(1) = 3;

查看代码

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 student_id,COUNT(1) from score where student_id  in (SELECT student_id from score where student_id!=2 and course_id in(SELECT course_id from score WHERE student_id=2) GROUP BY student_id HAVING COUNT(1)=(SELECT COUNT(1) from score where student_id=2 GROUP BY student_id)
) GROUP BY student_id HAVING COUNT(1)=(SELECT COUNT(1) from score where student_id=2 GROUP BY student_id);

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15、删除学习“叶平”老师课的score表记录；

 delete from score where course_id in (
        select cid from course left join teacher on course.teacher_id = teacher.tid where teacher.name = '叶平'
    )

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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；

由于insert 支持       inset into tb1(xx,xx) select x1,x2 from tb2;

insert into score(student_id, course_id, num) select sid,2,(select avg(num) from score where course_id = 2)
    from student where sid not in (
        select student_id from score where course_id = 2
    )

查看源码

 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；

select sc.student_id,
(SELECT num from score LEFT JOIN course on score.course_id=course.cid where course.cname='生物' and score.student_id=sc.student_id)as sy,
(SELECT num from score LEFT JOIN course on score.course_id=course.cid where course.cname='物理' and score.student_id=sc.student_id)as wl,
(SELECT num from score LEFT JOIN course on score.course_id=course.cid where course.cname='体育' and score.student_id=sc.student_id)as ty,
COUNT(1)
,avg(num)as PJ
from score as sc GROUP BY student_id ORDER BY pj asc;

查看源码

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；

SELECT course_id,MAX(num)as max_num ,MIN(num) as min_num from score GROUP BY course_id

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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；

思路：case when .. then

SELECT course_id,sum(case when score.num>60 then 1 else 0 END)/COUNT(1)*100 from score GROUP BY course_id

SELECT course_id,avg(num)as avg_num,sum(case when score.num>60 then 1 else 0 END)/COUNT(1)*100 as percent from score GROUP BY course_id ORDER BY avg_num desc,percent asc

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20、课程平均分从高到低显示（现实任课老师）；

SELECT avg(if(ISNULL(score.num),0,score.num))as percent ,teacher.tname,score.course_id from course 
LEFT JOIN teacher on course.teacher_id=teacher.tid 
LEFT JOIN score on score.course_id=course.cid 
GROUP BY score.course_id ORDER BY percent desc;

查看源码

21、查询各科成绩前三名的记录:(不考虑成绩并列情况)；

SELECT score.sid,score.course_id,score.num,t.first_num,t.second_num   from score LEFT JOIN
(SELECT sid,course_id,(SELECT num from score as s1 where s1.course_id = s2.course_id ORDER BY num desc limit 0,1) as first_num,
(SELECT num from score as s1 where s1.course_id = s2.course_id ORDER BY num desc limit 3,1) as second_num
 from score as s2)as t on score.sid=t.sid where score.num<= t.first_num and score.num>= t.second_num

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22、查询每门课程被选修的学生数；

SELECT course_id,COUNT(1) from score GROUP BY course_id

23、查询出只选修了一门课程的全部学生的学号和姓名；

SELECT score.student_id,student.sname from score LEFT JOIN student on score.student_id=student.sid  GROUP BY student_id HAVING COUNT(1)=1

查看源码

24、查询男生、女生的人数；

 select * from
    (select count(1) as man from student where gender='男') as A ,
    (select count(1) as feman from student where gender='女') as B

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25、查询姓“张”的学生名单；

select * from student where sname LIKE '张%'

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26、查询同名同姓学生名单，并统计同名人数；

SELECT sname,COUNT(1)as count from student GROUP BY sname

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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；

SELECT course_id ,avg(IF(ISNULL(num),0,num)) as avg_num from score GROUP BY course_id ORDER BY avg_num asc ,course_id DESC 

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；

SELECT student_id,course_id,COUNT(1), AVG(if(ISNULL(num),0,num))as avg_num from score LEFT JOIN student on score.student_id=student.sid GROUP BY student_id HAVING avg_num>85

查看源码

29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；

SELECT student.sname,score.num from score LEFT JOIN course on score.course_id=course.cid  LEFT JOIN student on score.student_id=student.sid  WHERE course.cname='生物' and score.num<60

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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；

SELECT score.student_id,student.sname,score.num from score LEFT JOIN student on score.student_id=student.sid where score.course_id=3 and score.num>80 

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31、求选了课程的学生人数

SELECT count(DISTINCT student_id) from score;

SELECT count(1) from (SELECT COUNT(1) from score GROUP BY student_id)as A;

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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；

SELECT student.sname,score.num from score LEFT JOIN course on score.course_id=course.cid LEFT JOIN teacher on course.teacher_id=teacher.tid  LEFT JOIN student on score.student_id=student.sid  WHERE teacher.tname='张磊老师' ORDER BY num DESC LIMIT 0,1;

查看源码

select sname,num from score    left join student on score.student_id = student.sid    where score.course_id in (select course.cid from course left join teacher on course.teacher_id = teacher.tid where tname='张磊老师') order by num desc limit 1;

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33、查询各个课程及相应的选修人数；

SELECT course.cname,count(1) FROM score LEFT JOIN course on score.course_id=course.cid GROUP BY course_id

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 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；

select DISTINCT s1.course_id,s2.course_id,s1.num,s2.num from score as s1, score as s2 where s1.num = s2.num and s1.course_id != s2.course_id;

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35、查询每门课程成绩最好的前两名；

 select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num

查看源码

36、检索至少选修两门课程的学生学号；

SELECT student_id from score GROUP BY student_id HAVING COUNT(course_id)>1

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37、查询全部学生都选修的课程的课程号和课程名；

SELECT course_id,course.cname from score LEFT JOIN course on score.course_id=course.cid GROUP BY course_id HAVING COUNT(1)=(SELECT COUNT(1) 

查看源码

38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；

SELECT * FROM student where sid not in(SELECT DISTINCT student_id from score WHERE score.course_id in
(SELECT cid from course LEFT JOIN teacher on course.teacher_id= teacher.tid WHERE teacher.tname='张磊老师'))

查看源码

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,course_id,COUNT(1)as num_1 from score where num<60 GROUP BY student_id HAVING num_1>=2

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40、检索“004”课程分数小于60，按分数降序排列的同学学号；

SELECT student_id,num from score where score.course_id=4 and num<90 ORDER BY num desc

查看源码

41、删除“002”同学的“001”课程的成绩；

delete from score where course_id = 1 and student_id = 2

标签：练习题,num,course,score,student,mysql,id,SELECT
From： https://www.cnblogs.com/yuhankeji/p/17241775.html