视图只读模式的创建,联合查询

1创建：create or replace (可对同一表名的表格数据进行多次修改) 

2只读模式（不可以进行修改）：with read only

create or replace view vw_feature2  as select g3e_fno,g3e_username  from g3e_feature where g3e_tooltip like '%低压配电房%' with  read only

3只要数据之间有交集，则可以进行数据的联合查询

create or replace vw_feature2 as select e.g3e_cno ,e.g3e_username ,s.g3e_fno,s.g3e_tooltip from g3e_component e,g3e_feature s where e.g3e_username =s.g3e_username ;