从间隔列中只取几天 - Postgresql

Question

我正在尝试从下面的间隔类型列中仅获取天数。

为此，我运行了以下查询，但它所做的只是将所有内容四舍五入到天，如下表所示：

select date_trunc('days', avg(d.date)) as Days_till_invite
from datamodel d

0 years 0 mons 173 days 0 hours 0 mins 0.00 secs
0 years 0 mons 173 days 0 hours 0 mins 0.00 secs
0 years 0 mons 173 days 0 hours 0 mins 0.00 secs
0 years 0 mons 173 days 0 hours 0 mins 0.00 secs
0 years 0 mons 173 days 0 hours 0 mins 0.00 secs
0 years 0 mons 172 days 0 hours 0 mins 0.00 secs
0 years 0 mons 172 days 0 hours 0 mins 0.00 secs
0 years 0 mons 172 days 0 hours 0 mins 0.00 secs
0 years 0 mons 172 days 0 hours 0 mins 0.00 secs
0 years 0 mons 172 days 0 hours 0 mins 0.00 secs
0 years 0 mons 171 days 0 hours 0 mins 0.00 secs
0 years 0 mons 171 days 0 hours 0 mins 0.00 secs
0 years 0 mons 171 days 0 hours 0 mins 0.00 secs
0 years 0 mons 170 days 0 hours 0 mins 0.00 secs
0 years 0 mons 170 days 0 hours 0 mins 0.00 secs

期望的输出

理想情况下，输出应该是：（仅提取日期值）

173
173
173
173
172 
[...]

Answer 1

可能最简单的方法是使用epoch：

select extract(epoch from d.date) / (24 * 60 * 60) as days