s4 mysql基础 练习题
MySQL一（练习题）
____oldboy fullstack4
参考资料：
mysql表操作练习题：
http://www.cnblogs.com/wupeiqi/articles/5729934.html
练习题表：
http://images2015.cnblogs.com/blog/425762/201608/425762-20160803224643778-2071849037.png
MySQL练习题参考答案
https://www.cnblogs.com/wupeiqi/articles/5748496.html
- 练习题
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 score.student_id,student.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")
--
--
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
-- 查询没有学全所有课的同学的学号、姓名；
11、查询没有学全所有课的同学的学号、姓名；
-- 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”同学所有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；
-- 获取和方少伟选课个数相同的通许
-- 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
-- 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；
-- 1 90 80 99
-- 2 90 80 99
-- 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),min(num)+1,case when min(num) <10 THEN 0 ELSE min(num) END as c 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),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 jgl
from score GROUP BY course_id order by AVG(num) asc,jgl desc;
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