Mysql数据库二三

1、 导入hellodb.sql生成数据库

(1) 在students表中，查询年龄大于25岁，且为男性的同学的名字和年龄

MariaDB [db1]> select name,age from student where age>25 AND gender='M';

 

 

 

(2) 以ClassID为分组依据，显示每组的平均年龄

select ClassID,avg(age) from student where ClassID is not null group by ClassID;

 

 

 

(3) 显示第2题中平均年龄大于30的分组及平均年龄

select ClassID,avg(age) as avgage from student where ClassID is not null group by classid having avgage>30;

 

 

 

(4) 显示以L开头的名字的同学的信息

MariaDB [db1]> select * from student where name like '%L%';

 

 

 

2、数据库授权magedu用户，允许192.168.1.0/24网段可以连接mysql

 

create user magedu@'192.168.1.%';

flush privileges;

grant all privileges on hellodb.* to 'magedu'@'192.168.0.%';