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文章来源：https://www.toymoban.com/news/detail-567882.html
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;
文章来源地址https://www.toymoban.com/news/detail-567882.html
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