PostgreSQL得出两个timestamp的秒数差值

sql语句

SELECT EXTRACT(EPOCH FROM (TIMESTAMP '2017-12-16 12:21:13'- TIMESTAMP '2017-12-15 12:21:00'));

=>

 86413

计算两个时间的差值更新另一个时间字段

UPDATE your_table
SET this_time=(EXTRACT(EPOCH FROM (time_a-time_b)));