数据库多表查询作业

创建数据库

插入数据

mysql> insert into student values(901,'张老大','男',1985,'计算机系','北京市海淀区'),
    -> (902,'张老二','男',1986,'中文系','北京市昌平市'),
    -> (903,'张三','女',1990,'中文系','湖南省永州市'),                                           -> (904,'李四','男',1990,'英语系','辽宁省阜新市'),                                           -> (905,'王五','女',1991,'英语系','福建省厦门市'),
    -> (906,'王六','男',1988,'计算机系','湖南省衡阳市');

mysql> insert into score values(null,901,'计算机',98),
    -> (null,901,'英语',80),
    -> (null,902,'计算机',65),
    -> (null,902,'中文',88),
    -> (null,903,'中文',95),
    -> (null,904,'计算机',70),
    -> (null,904,'英语',92),
    -> (null,905,'英语',94),
    -> (null,906,'计算机',90),
    -> (null,906,'英语',85);

1.查询student表的所有记录

mysql> select * from student;

2.查询student表的第2条到4条记录

mysql> select * from student limit 1,3;

3.从student表查询所有学生的学号（id）、姓名
（name）和院系（department）的信息

mysql> select id as 学号,name as 姓名,department as 院系 from student;

4.从student表中查询计算机系和英语系的学生的信息

mysql> select * from student where department='计算机系' or department='英语系';

5.从student表中查询年龄18~22岁的学生信息

mysql> select *,year(curdate())-birth as age from student where year(curdate())-birth between 18 and 22;

6.从student表中查询每个院系有多少人

mysql> select department as 院系,count(*) as 人数 from student group by department;

7.从score表中查询每个科目的最高分

mysql> select c_name as 科目,max(grade) as 最高分 from score group by c_name;

8.查询李四的考试科目（c_name）和考试成绩（grade）

mysql> select name as 姓名,c_name as 科目,grade as 成绩 from student
    -> inner join score on student.id=score.stu_id
    -> where name='李四';

9.用连接的方式查询所有学生的信息和考试信息

mysql> select * from student iudent inner join score on student.id=score.stu_id;

10.计算每个学生的总成绩

mysql> select name as 姓名,sum(grade) as 总成绩 from student
    -> inner join score on student.id=score.stu_id
    -> group by name;

11.计算每个考试科目的平均成绩

mysql> select avg(grade) from score group by c_name;

12.查询计算机成绩低于95的学生信息

mysql> select * from student
    -> inner join (select stu_id,c_name,grade from score where grade<95 and c_name='计算机') as stu
    -> on student.id=stu.stu_id;

13.查询同时参加计算机和英语考试的学生的信息

获取同时考计算机和英语的学生ID

select * from score where c_name='英语') as sc2 where sc1.stu_id=sc2.stu_id

根据ID获取学生信息

mysql> select * from student inner join (select sc1.stu_id from (select * from score where c_name='计算机') as sc1,(select * from score where c_name='英语') as sc2 where sc1.stu_id=sc2.stu_id) as sc on student.id=sc.stu_id;

14.将计算机考试成绩按从高到低进行排序

mysql> select * from score where c_name='计算机' order by grade desc;

15.从student表和score表中查询出学生的学号，然后合并查询结果

mysql> select student.id,score.stu_id from student inner join (select distinct stu_id from score) as score on student.id=score.stu_id;

16.查询姓张或者姓王的同学的姓名、院系和考试科目及成绩

mysql> select stu.name as 姓名, stu.department as 院系, score.c_name as 科目,score.grade as  成绩
    -> from score inner join
    -> (select * from student where name like '张%' or name like '王') as stu
    -> on score.stu_id=stu.id;

17.查询都是湖南的学生的姓名、年龄、院系和考试科目及成绩

mysql> select stu.name as 姓名,year(curdate())-stu.birth as age,stu.department as 院系,score.c_name as 科目,score.grade as 成绩
    -> from score
    -> inner join
    -> (select * from student where address like '%湖南%') as stu
    -> on score.stu_id=stu.id;