PG时间相减

用于获取两个时间相差

audit=# select age('2020-01-01 17:53:02' :: TIMESTAMP , '2020-01-01 17:46:20' :: TIMESTAMP);
   age    
----------
 00:06:42
(1 row)
-- 等价于
select '2020-01-01 17:53:02' :: TIMESTAMP -'2020-01-01 17:46:20' :: TIMESTAMP;

2、时间戳

可能我们需要获取多少秒；即上面的“ 6 min 42 sec；应该是 402 s

audit=# select EXTRACT(epoch FROM '2020-01-01 17:53:02' :: TIMESTAMP ) - EXTRACT(epoch FROM '2020-01-01 17:46:20' :: TIMESTAMP );
 ?column? 
----------
      402
(1 row)