• 0608mysql练习:查询3


    2、查询“生物”课程比“物理”课程成绩高的所有学生的学号;

    select a.student_id from(select * from score where course_id = (select course_id from course where course_name = '生物'))as a inner join(select * from score where course_id = (select course_id from course where course_name = '物理'))as b on a.student_id = b.student_id and a.score_number > b.score_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.student_id,a.student_name,count(course_id),ifnull(sum(score_number),0) from student as a left join score as b on a.student_id = b.student_id group by a.student_id

    5、查询姓“马”的老师的个数;

    select count(*) from teacher where teacher_name like '马%'

    6、查询没学过“俞敏洪”老师课的同学的学号、姓名;

    select student_id,student_name from student where student_id not in (select student_id from score natural join course where teacher_id = (select teacher_id from teacher where teacher_name = '马化腾'))

    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_id,student_name from student where student_id in (select  student_id from score group by student_id having group_concat(course_id) like '1,2%') ;

    8、查询学过“马云”老师所教的所有课的同学的学号、姓名;

    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;

    10、查询有课程成绩小于60分的同学的学号、姓名;

    11、查询没有学全所有课的同学的学号、姓名;

    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;

    21、查询每门课程的任课老师、课程名称和课程平均分,并按照分数从高到低排序;

    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、查询选修了课程的学生人数

    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;

    36、查询至少选修两门课程的学生学号;

    37、查询全部学生都选修的课程的课程号和课程名;

    39、查询两门以上不及格课程的同学的学号及其平均成绩;



        2、查询“生物”课程比“物理”课程成绩高的所有学生的学号;
        思路:
            获取所有有生物课程的人(学号,成绩) - 临时表
            获取所有有物理课程的人(学号,成绩) - 临时表
            根据【学号】连接两个临时表:
                学号  物理成绩   生物成绩
         
            然后再进行筛选
         
                select A.student_id,sw,ty from
         
                (select student_id,num as sw from score left join course on score.course_id = course.cid where course.cname = '生物') as A
         
                left join
         
                (select student_id,num  as ty from score left join course on score.course_id = course.cid where course.cname = '体育') as B
         
                on A.student_id = B.student_id where sw > if(isnull(ty),0,ty);
         
        3、查询平均成绩大于60分的同学的学号和平均成绩;
            思路:
                根据学生分组,使用avg获取平均值,通过having对avg进行筛选
         
                select student_id,avg(num) from score group by student_id having avg(num) > 60
         
        4、查询所有同学的学号、姓名、选课数、总成绩;
         
            select score.student_id,sum(score.num),count(score.student_id),student.sname
            from
                score left join student on score.student_id = student.sid
            group by score.student_id
         
        5、查询姓“李”的老师的个数;
            select count(tid) from teacher where tname like '李%'
         
            select count(1) from (select tid from teacher where tname like '李%') as B
         
        6、查询没学过“叶平”老师课的同学的学号、姓名;
            思路:
                先查到“李平老师”老师教的所有课ID
                获取选过课的所有学生ID
                学生表中筛选
            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'
                )
            )
         
        7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名;
            思路:
                先查到既选择001又选择002课程的所有同学
                根据学生进行分组,如果学生数量等于2表示,两门均已选择
         
            select student_id,sname from
         
            (select student_id,course_id from score where course_id = 1 or course_id = 2) as B
         
            left join student on B.student_id = student.sid group by student_id HAVING count(student_id) > 1
         
        8、查询学过“叶平”老师所教的所有课的同学的学号、姓名;
         
            同上,只不过将001和002变成 in (叶平老师的所有课)
         
        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;
            同第1题
         
        10、查询有课程成绩小于60分的同学的学号、姓名;
         
            select sid,sname from student where sid in (
                select distinct student_id from score where num < 60
            )
         
        11、查询没有学全所有课的同学的学号、姓名;
            思路:
                在分数表中根据学生进行分组,获取每一个学生选课数量
                如果数量 == 总课程数量,表示已经选择了所有课程
         
                select student_id,sname
                from score left join student on score.student_id = student.sid
                group by student_id HAVING count(course_id) = (select count(1) 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;
            思路:
                获取 001 同学选择的所有课程
                获取课程在其中的所有人以及所有课程
                根据学生筛选,获取所有学生信息
                再与学生表连接,获取姓名
         
                select student_id,sname, count(course_id)
                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 student_id = 1) group by student_id
         
        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;
                先找到和001的学过的所有人
                然后个数 = 001所有学科     ==》 其他人可能选择的更多
         
                select student_id,sname, count(course_id)
                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 student_id = 1) group by student_id having count(course_id) = (select count(course_id) from score where student_id = 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;
         
                个数相同
                002学过的也学过
         
                select student_id,sname from score left join student on score.student_id = student.sid where student_id in (
                    select student_id from score  where student_id != 1 group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
                ) and course_id in (select course_id from score where student_id = 1) group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
         
        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'
            )
         
        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;
            思路:
                由于insert 支持
                        inset into tb1(xx,xx) select x1,x2 from tb2;
                所有,获取所有没上过002课的所有人,获取002的平均成绩
         
            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
            )
         
        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(sc.course_id),
                avg(sc.num)
            from score as sc
            group by student_id desc        
         
        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;
         
        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, avg(num) as avgnum,sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent from score group by course_id order by avgnum asc,percent desc;
         
        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)),teacher.tname from course
            left join score on course.cid = score.course_id
            left join teacher on course.teacher_id = teacher.tid
         
            group by score.course_id
         
        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,
                (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 3,1) 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
         
        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 student.sid, student.sname, count(1) from score
         
            left join student on score.student_id  = student.sid
         
             group by course_id having count(1) = 1
         
        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
         
        25、查询姓“张”的学生名单;
            select sname from student where sname like '张%';
         
        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;
         
        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 from score group by course_id order by avg     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,sname, avg(if(isnull(num), 0 ,num)) from score left join student on score.student_id = student.sid group by student_id;
         
        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 score.num < 60 and course.cname = '生物'
         
        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 * from score where score.student_id = 3 and score.num > 80
         
        31、求选了课程的学生人数
         
            select count(distinct student_id) from score
         
            select count(c) from (
                select count(student_id) as c from score group by student_id) as A
         
        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 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;
         
        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;
         
        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;
         
        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
         
        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(student_id) > 1
         
        37、查询全部学生都选修的课程的课程号和课程名;
            select course_id,count(1) from score group by course_id having count(1) = (select count(1) from student);
         
        38、查询没学过“叶平”老师讲授的任一门课程的学生姓名;
            select student_id,student.sname from score
            left join student on score.student_id = student.sid
            where score.course_id not in (
                select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '张磊老师'
            )
            group by student_id
         
        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(1) from score where num < 60 group by student_id having count(1) > 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 student_id from score where num< 60 and course_id = 4 order by num desc;
         
        41、删除“002”同学的“001”课程的成绩;
            delete from score where course_id = 1 and student_id = 2

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  • 原文地址:https://www.cnblogs.com/zhangbaozhong/p/9158357.html
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