/*视图的必要性

create view population_all_view

as

 select xxxx 详细信息 from qgck  where rownum<500 -- sql语句不易读懂

create view population_all_view

as

select * from qgck where rownum<500;-- sql语句超出负载。

*/

select * from scott.emp;

--视图的创建

   查询员工编号、员工名及所在部门的名称

   create or replace  view  emp_basic_info_view

   as

  select  scott.emp.empno as 员工编号,scott.emp.ename as 员工名,

  scott.dept.dname as 部门名  from scott.emp ,scott.dept

  where scott.emp.deptno = scott.dept.deptno

  --查询视图

  select * from emp_basic_info_view

delete from system.emp_basic_info_view where 员工编号='8000';

--练习1