PostgreSQL视图：引用另一个计算字段中的一个计算字段

Question

我和#1895500有同样的问题，但PostgreSQL不是MySQL。

如何定义具有计算字段的视图，例如：

 (mytable.col1 * 2) AS times_two

...并创建另一个基于第一个的计算字段：

 (times_two * 2) AS times_four

...

Answer 1

根据公式的重量，您可以使用子查询：

select inner.*, times_two * 2 from
(select mycol * 2 as times_two from table) sub

或重写计算：

select mycol * 2, mycol * 2 * 2 from table

Answer 2

  

使用此声明

 
CREATE  VIEW  view_name as  SELECT  column_name*2 as new_col1 , column_name*4 as new_col2  from table_name ; 

select * from view_name ; 

If you want use this view column values. use following things 

create view new_viwe as select new_col1*2 as final_column from view_name ; 

select * from new_view ;