创建一个名为 see 的视图，它可以获得 查询所有student表中age<18的数据 create view see as select * from student where age < 18
删除一个名为see的视图 drop view see
修改see视图，把它改成 查询 老师表teacher 中级别level大于2的数据 alter view see as select * from teacher where level > 2
查看视图see的详细情况 desc see
查看视图see的创建语句 show create view see
