MySQL-----操作练习

 

一、表关系

请创建如下表,并创建相关约束

 

 

二、操作表

1、自行创建测试数据

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 score.sid,score.student_id,course.cname,score.num from score LEFT JOIN course on score.course_id=course.cid where course.cname="生物") as A INNER JOIN (select score.sid,score.student_id,course.cname,score.num from score LEFT JOIN course on score.course_id=course.cid where course.cname="物理") as B on A.student_id = B.student_id where A.num > B.num

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(num) from score GROUP BY student_id HAVING avg(num) > 60;

  --如何要在显示学生姓名,就要讲刚刚的结果建成临时表,在连表学生表,left join student,在临时表中有聚合函数avg(),所以给avg起别名才能用,起aaa。

  SELECT B.studetn_id,student.name,B.aaa from (select student_id,avg(num) as aaa from score GROUP BY student_id HAVING avg(num) > 60)as B  left join student on B.student_id=student.sid;

4、查询所有同学的学号、姓名、选课数、总成绩;

  --先使score成绩表和学生表student连起来,

  select * from score left join student on score.student_id=student.sid

  --拿到学生id和姓名

  select score.student_id,studnet.sname from score LEFT JOIN student on score.student_id=student.sid

  --分组,

  select * from score left join student on score.student_id=student.sid GROUP BY score.student_id

  --最终

  select score.student_id,studnet.sname,count(student_id),sum(num) 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;

6、查询没学过“叶平”老师课的同学的学号、姓名;

  --先查老师表

  select * from teacher;

  --连表,老师表和课程表,查叶平的任教课程id

  select  course.cid  from course  left  join  teacher  on  course.teacher_id=teacher_tid  where  teacher.name = "叶平老师";

  --去成绩表拿没有叶平课的结果

  select * from score where course_id not in (2,4);         in里可以加sql语句。

  --最终

  select student.sid, student.sname  from student where sid not in (

    select student_id from score where course_id in (select course.cid from course

      left join teacher on course.teacher_id = teacher.tid where

        teacher.tname = "叶平老师")group by student_id); 

7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名;

  --先取得成绩表

  select * from score 

  --过滤001和002 并分组

  select score.student_id, studnet.sname from score left join student on score.student_id=student.sid where course_id = 1 or course_id = 2 GROUP BY student_id HAVING count(course_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;

  select student_id 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(course_id) = (select count(cid) from course left JOIN teacher on course.teacher_id = teacher.tid where teacher.tname = "李平老师")

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;

  select student_id from score where num < 60 GROUP BY student_id
  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;

  select student_id,count(1) from score GROUP BY student_id  HAVING count(1) < (select count(cid) 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 course_id from score where student_id = 1;
  select student_id from score 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”同学所选课程中任意一门课的其他同学学号和姓名;

  select course_id from score where student_id = 1;
  select student_id,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(1) = (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;

  select count(1) from score where student_id = 1;

  select student_id from score where student_id in (
  select student_id from score where student_id !=1 GROUP BY student_id HAVING count(1) = (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(1) = (select count(1) from score where student_id = 1)

insert into tb(student_id,course_id,num)

  select student_id,2,(SELECT AVG(num) from score where course_id = 2) from score where course_id != 2

15、删除学习“叶平”老师课的SC表记录;

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;

36、检索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;

38、查询没学过“叶平”老师讲授的任一门课程的学生姓名;

39、查询两门以上不及格课程的同学的学号及其平均成绩;

40、检索“004”课程分数小于60,按分数降序排列的同学学号;

41、删除“002”同学的“001”课程的成绩;

 

posted @ 2017-08-10 10:18  王先生是胖子  阅读(205)  评论(0编辑  收藏  举报