Python/ MySQL练习题（一）

Python/ MySQL练习题（一）

查询“生物”课程比“物理”课程成绩高的所有学生的学号

 SELECT
     *
 FROM
     (
         SELECT
             *
         FROM
             course
         LEFT JOIN score ON score.course_id = course.cid
         WHERE
             course.cname = '生物'
     ) AS A
 INNER JOIN (
     SELECT
         *
     FROM
         course
     LEFT JOIN score 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

查询平均成绩大于60分的同学的学号和平均成绩

 SELECT
     B.student_id,
     student.sname,
     B.cc
 FROM
     (
         SELECT
             student_id,
             num,
             avg(num) AS cc
         FROM
             score
         GROUP BY
             student_id
         HAVING
             avg(num) > 60
     ) AS B
 LEFT JOIN student ON B.student_id = student.sid

查询所有同学的学号、姓名、选课数、总成绩

 SELECT
     student_id,
     student.sname,
     count(score.course_id)as cc,
     sum(num)as cj
 FROM
     student
 LEFT JOIN score ON score.student_id = student.sid
 GROUP BY
     score.student_id

查询姓“李”的老师的个数

 SELECT * from teacher where tname like '李%'

查询没学过“李平”老师课的同学的学号、姓名

 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 teacher.tid = course.teacher_id
         WHERE
             tname = '李平老师'
     ) GROUP BY student_id)

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,B.sname FROM (SELECT score.student_id,student.sname,course_id
  from score LEFT JOIN student on student.sid=score.student_id where score.course_id='')as A
  LEFT JOIN(SELECT score.student_id,student.sname,course_id
  from score LEFT JOIN student on student.sid=score.student_id where score.course_id='')as B
  on A.student_id=B.student_id
 where A.course_id=1 and B.course_id=2;

 查询学过“李平”老师所教的所有课的同学的学号、姓名

 SELECT
     student.sid,
     student.sname
 FROM
     student
 WHERE
     student.sid NOT IN (
         SELECT
             student.sname
         FROM
             student
         WHERE
             student.sid IN (
                 SELECT
                     course.cid
                 FROM
                     course
                 LEFT JOIN teacher ON teacher.tid = course.teacher_id
                 WHERE
                     teacher.tname = '李平老师'
             )
     )

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
     student.sid,
     student.sname
 FROM
     (
         SELECT
             *
         FROM
             score
         WHERE
             score.course_id = ''
     ) AS A
 LEFT JOIN (
     SELECT
         *
     FROM
         score
     WHERE
         score.course_id = ''
 ) AS B ON A.student_id = B.student_id
 LEFT JOIN student ON student.sid = B.student_id
 WHERE
     A.num < B.num

查询有课程成绩小于60分的同学的学号、姓名

 SELECT
     student.sid,
     student.sname
 FROM
     score
 LEFT JOIN course ON course.cid = score.course_id
 LEFT JOIN student ON student.sid = score.student_id
 WHERE
     score.num < 60
 GROUP BY
     student_id

查询没有学全所有课的同学的学号、姓名

 SELECT
     student.sid,
     student.sname
 FROM
     student
 WHERE
     student.sid NOT IN (
         SELECT
             student.sid
         FROM
             score
         LEFT JOIN course ON course.cid = score.course_id
         LEFT JOIN student ON student.sid = score.student_id
         GROUP BY
             score.student_id
         HAVING
             count(course_id) = (SELECT COUNT(cid) FROM course)
     )

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
 *
  FROM
     score
     LEFT JOIN student on score.student_id = student.sid
     LEFT JOIN course ON course.cid = score.course_id
  WHERE student_id != 1 AND
 score.course_id  in  (
         SELECT
             course_id
         FROM
             score
         WHERE
             student_id = 1
 )
 GROUP BY student_id

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 student_id from score where student_id!=1 and course_id IN
 (select course_id from score where student_id =1 GROUP BY course_id)
 GROUP BY student_id

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,
     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
     )

删除学习“李平”老师课的SC表记录

  DELETE FROM score where score.course_id IN
  (SELECT course_id from course LEFT JOIN teacher  on teacher.tid=course.teacher_id
  LEFT JOIN score on score.course_id=course.cid
  LEFT JOIN student  on score.student_id=student.sid
  WHERE teacher.tname='李平老师'
 GROUP BY course_id;)

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

 insert into score (student_id,course_id,num)SELECT student_id,1,FLOOR(avg(num))
 (SELECT student_id from score where course_id !=2
 SELECT FLOOR(avg(num))from score where course_id = 2)

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        

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 student_id,MAX(num),MIN(num) from score GROUP BY course_id

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

 SELECT
     course_id,
     avg(num) AS nn,
     sum(
         CASE
         WHEN num < 60 THEN
             0
         ELSE
             1
         END
     ),
     SUM(1),
     sum(
         CASE
         WHEN num < 60 THEN
             0
         ELSE
             1
         END
     ) / SUM(1) AS pj
 FROM
     score
 GROUP BY
     course_id
 ORDER BY
     avg(num) DESC

课程平均分从高到低显示（现实任课老师）

 SELECT score.course_id,course.cname,avg(num),teacher.tname from score LEFT JOIN course on course.cid=score.course_id
 LEFT JOIN teacher on teacher.tid=course.teacher_id
 GROUP BY course_id
 
 HAVING avg(num)
 ORDER BY avg(num) DESC