PostgreSQL的格式後柱

Question

這個查詢尋找連續行之間的差別的偉大工程：

select id, created_at, created_at - lag(created_at, 1) 
over (order by created_at) as diff 
from fistbumps where bumper_id = 2543 
and created_at between '2012-01-11' and '2012-01-12' order by created_at; 

...但出來的結果一樣：

id |   created_at   |  diff  
--------+----------------------------+----------------- 
197230 | 2012-01-11 00:04:31.774426 | 
197231 | 2012-01-11 00:04:32.279181 | 00:00:00.504755 
197232 | 2012-01-11 00:04:33.961665 | 00:00:01.682484 
197233 | 2012-01-11 00:04:36.506685 | 00:00:02.54502 

什麼是真正的常規是，如果我可以將該差異列格式化爲秒和毫秒（例如2.54502）。我嘗試使用date_trunc（）和extract（），但我似乎無法得到正確的語法。

Answer 1

created_at - lag（create_at）的結果是interval類型的值。

可以使用extract(epoch from interval_value)

所以你的情況這將是得到一個interval的秒：

extract(epoch from (created_at - lag(created_at, 1)))