如何在postgresql中添加天数datetime

我有一个下面的表项目。

id title        created_at                     claim_window
1  Project One  2012-05-08 13:50:09.924437     5
2  Project Two  2012-06-01 13:50:09.924437     10

A)我想找到计算期限的最后期限= created_at claim_window(天数)。

像下面的东西。

id title        created_at                     claim_window deadline
1  Project One  2012-05-08 13:50:09.924437     5            2012-05-13 13:50:09.924437
2  Project Two  2012-06-01 13:50:09.924437     10           2012-06-11 13:50:09.924437

B]我还想找到那些截止日期已过的项目

id title        created_at                     claim_window deadline
1  Project One  2012-05-08 13:50:09.924437     5            2012-05-13 13:50:09.924437

我尝试像下面的东西。

SELECT * FROM "projects" WHERE (DATE_PART('day',Now()- created_at) >= (claim_window+1))

但由于某种原因，它不工作。

这将给你的最后期限：

select id,title,created_at + interval '1' day * claim_window as deadline
from projects

要获得截止日期已过的所有项目，请使用：

select *
from (
  select id,created_at + interval '1' day * claim_window as deadline
  from projects
) t
where localtimestamp at time zone 'UTC' > deadline