Postgresql-按时间戳和车辆id分组

我有一张有汽车记录的桌子:

table: cars

columns:
car_id | timestamp | km_driven

我在跑步 PostgreSQL 9.6 .

我该怎么做:

SELECT timestamp, car_id, km_driven_within_the_hour FROM cars

我想 GROUP BY 我的 timestamp 因此,每小时记录的所有记录按每辆车分组,然后 km_driven_within_the_hour SUM “艾德在那一小时内就到了。

我试过:

SELECT timestamp, car_id, SUM(km_driven) AS km_driven_within_the_hour
FROM cars
GROUP BY trunc(EXTRACT(hour from timestamp)), car_id

给我错误:

ERROR:  function pg_catalog.date_part(unknown, text) does not exist

以及转换时间戳:

SELECT timestamp, car_id, SUM(km_driven) AS km_driven_within_the_hour
FROM cars
GROUP BY trunc(EXTRACT(hour from timestamp::timestamp)), car_id

给我:

ERROR:  column "cars.timestamp" must appear in the GROUP BY clause or be used in an aggregate function