-- 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,sw,ty from -- -- (select student_id,num as sw from score INNER 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 INNER join course on score.course_id = course.cid where course.cname = '物理') 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； -- select student_id,avg(number) from l5 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 student.sid,student.sname,count(score.student_id),sum(num) -- from score LEFT JOIN student on score.student_id=student.sid GROUP BY -- student_id; -- 5.查询姓“李”的老师的个数； -- select count(tid) from l3 where tname like "李%"; -- 6.查询没学过“叶平”老师课的同学的学号、姓名； -- SELECT student.sid,student.sname from student where sid not in ##通过学生表查询没有该课程的学生id和姓名 -- (select student_id from score where course_id in(##成绩表中查出有此课程的学生id -- SELECT course.cid from course -- LEFT JOIN teacher on course.teacher_id=teacher.tid where teacher.tname="李平老师"##课程表和老师表连表， -- 求出李平老师的课程 -- ) -- 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； -- SELECT A.student_id,A.sname FROM -- (SELECT score.student_id,student.sname from score LEFT JOIN student on score.student_id=student.sid where course_id=1) as A, -- (SELECT score.student_id,student.sname from score LEFT JOIN student on score.student_id=student.sid where course_id=2) as B -- where A.student_id=B.student_id -- -- 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.sid,student.sname from student where sid in ##通过学生表查询有该课程的学生id,姓名 -- (select student_id from score where course_id in(##成绩表中查出有此课程的学生id -- SELECT course.cid from course -- LEFT JOIN teacher on course.teacher_id=teacher.tid where teacher.tname="李平老师"##课程表和老师表连表， -- -- 求出李平老师的课程 -- ) -- GROUP BY student_id) HAVING count(course_id)=(SELECT count(course.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； -- SELECT sid,sname from student INNER JOIN -- (select student_id,score.num from score where course_id=2) as A on A.student_id=student.sid -- -- INNER JOIN(select student_id,score.num from score where course_id=1) as B on B.student_id=student.sid -- where A.num<B.num -- 10.查询有课程成绩小于60分的同学的学号、姓名； -- select l5.sid,l2.sname from l5,l2 where l5.student_id=l2.sid and l5.number < 60; -- 11、查询没有学全所有课的同学的学号、姓名； -- select student_id,sname,course_id 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； -- SELECT student_id,sname 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; -- SELECT * from score -- 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 student_id,sname 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(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； -- -- 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； -- -- 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 -- student_id, -- (select num from score as s2 where s2.student_id=s1.student_id and course_id = 1) as 语文, -- (select num from score as s2 where s2.student_id=s1.student_id and course_id = 2) as 数学, -- (select num from score as s2 where s2.student_id=s1.student_id and course_id = 3) as 英语 -- from score as s1; -- 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),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； -- SELECT course_id,avg(num) FROM score GROUP BY course_id ORDER BY avg(num)asc -- SELECT course_id,avg(num),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 f from score ORDER BY avg(num) ASC, -- f DESC; -- SELECT * from score -- -- 20.课程平均分从高到低显示（现实任课老师）； -- SELECT A.course_id,teacher.tname,A.cc from teacher INNER JOIN -- (SELECT teacher_id,course_id,avg(num)as cc from score LEFT JOIN course on score.course_id=course.cid GROUP BY course_id )as A -- ON teacher.tid=A.teacher_id -- ORDER BY A.cc desc -- 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 corse_id,count(student_id) as count from l5 group by corse_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_id,sname,course_id from score LEFT JOIN student on score.student_id=student.sid -- -- GROUP BY student_id HAVING count(1)=1 -- 24、查询男生、女生的人数； -- select count(sid),gender from l2 group by gender; -- -- 25、查询姓“张”的学生名单； -- select * from l2 where sname like "张%"; -- -- 26、查询同名同姓学生名单，并统计同名人数； -- select count(sid),sname from l2 group by sname having count(sid)>1; -- 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 corse_id,cname,avg(number) from l4 left l5 on l4.cid = l5.corse_id order by avg(number) asc; -- 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(number) from l5,l2 group by student_id having avg(number) > 85; -- -- 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_id,sname,num from score LEFT JOIN student on score.student_id=student.sid where num<60 and course_id in -- (SELECT cid from course LEFT JOIN score on course.cid=score.course_id where cname="生物" ); -- -- SELECT * FROM score -- 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 student_id,sname,num from score LEFT JOIN student on score.student_id=student.sid where course_id=3 -- and num>80; -- SELECT * from score -- 31、求选了课程的学生人数 -- SELECT count(course_id) from score GROUP BY student_id; -- SELECT course_id from score GROUP BY student_id; -- -- SELECT * from score -- -- 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； -- select course_id,COUNT(student_id) from score 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 course_id,MAX(num) from score GROUP BY course_id -- 36、检索至少选修两门课程的学生学号； -- SELECT student_id,course_id from score GROUP BY student_id HAVING count(course_id)>=2 -- 37、查询全部学生都选修的课程的课程号和课程名； -- SELECT student_id,course_id,course.cname from score LEFT JOIN course on score.course_id=course.cid GROUP BY student_id -- 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,avg(num) 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,course_id,num from score where course_id=4 and num<60 ORDER BY num DESC -- 41、删除“002”同学的“001”课程的成绩； -- DELETE from score where student_id=2 and corse_id=1