第十三周

1、如何将 hellodb_innodb.sql导入到数据库中

将hellodb_innodb.sql上传到服务器上

mysql < hellodb_sql

 

2、在学生表中，查询年龄大于25岁，且为男性的同学的名字和年龄

MariaDB [hellodb]> select name,age  from students where age > 25 and gender = 'm';

 

 

3、在学生表中，以ClassID为分组依据，查询显示每组的平均年

select classid,avg(age) from students group by classid;

 

 

4、显示第2题中平均年龄大于30的分组及平均年龄

MariaDB [hellodb]> select classid,avg(age) from (select classid,age from students where age > 25 and gender='M')as alias group by classid having avg(age) > 30 ;

 

5、显示以L开头的名字的同学的信息

MariaDB [hellodb]> select * from students where name like 'L%';

 

6、显示老师ID非空的同学的相关信息

MariaDB [hellodb]> select * from students where teacherid is not null;

 

7、students表中，查询以年龄排序后的数据，并且显示年龄最大的前10位同学的信息

 MariaDB [hellodb]> select * from students order by age desc limit 10;

 

8、students表中，查询年龄大于等于20岁，小于等于25岁的同学的信息

MariaDB [hellodb]> select * from students where 20<=age and age <=25;

 

9、以ClassID分组，显示每班的同学的人数 

MariaDB [hellodb]> select classid as 班级 ,count(stuid) as 学生人数 from students group by classid;

 

10、以ClassID分组，显示其平均年龄大于25的班级

MariaDB [hellodb]> select classid,avg(age) from students group by classid having avg(age)>25;