1、如何将 hellodb_innodb.sql导入到数据库中
mysql -u root -p123456 < hellodb_innodb.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
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龄
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
select ClassID,avg(age) as xs from (select ClassID,age from students where age > 25 and gender='M')as qwer group by ClassID having avg(age)>30;
5、显示以L开头的名字的同学的信息
select * from students where name like 'l%';
6、显示老师ID非空的同学的相关信息
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
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
select * from students where age between 20 and 25;
9、以ClassID分组，显示每班的同学的人数
select ClassID,count(*) from students group by ClassID;
10、以ClassID分组，显示其平均年龄大于25的班级
select classid,avg(age) from students group by classid having avg(age)>30;