一、查询数据 

ymysql-面试50题-2-CSDN博客

二、问题

21.查询男生、女生人数

mysql> select ssex, count(*) from student
    -> group by ssex;

22.查询名字中含有「风」字的学生信息

mysql> select *
    -> from student
    -> where student.Sname like '%风%'
    -> ;

23.查询同名同性学生名单，并统计同名人数

mysql> select sname, count(*) from student
    -> group by sname
    -> having count(*)>1;

24.查询 1990 年出生的学生名单

mysql> select *
    -> from student
    -> where YEAR(student.Sage)=1990;

25.查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

mysql> select sc.CId,avg(sc.score) from sc,course
    -> group by sc.cid
    -> order by avg(sc.score) desc,cid asc;

26.查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩

mysql> select student.sid, AVG(sc.score) as aver from student, sc
    -> where student.sid = sc.sid
    -> group by sc.sid
    -> having aver > 85;

27.查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

mysql> select student.sname, sc.score from student, sc, course
    -> where student.sid = sc.sid
    -> and course.cid = sc.cid
    -> and course.cname = "数学"
    -> and sc.score < 60;

28.查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

mysql> select student.sname, cid, score from student
    -> left join sc
    -> on student.sid = sc.sid;

29查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数

mysql> select student.sname, course.cname,sc.score from student,course,sc
    -> where sc.score>70
    -> and student.sid = sc.sid
    -> and sc.cid = course.cid;

30.查询不及格的课程

mysql> select DISTINCT sc.CId
    -> from sc
    -> where sc.score <60;