За да можете да изберете всички колони, а не само object_id
и MAX(event_timestamp)
, можете да използвате DISTINCT ON
SELECT DISTINCT ON (object_id)
object_id, event_timestamp ---, more columns
FROM test_select
ORDER BY object_id, event_timestamp DESC ;
Ако искате резултатите да са подредени по event_timestamp DESC
а не по object_id
, трябва да го включите в извлечена таблица или CTE:
SELECT *
FROM
( SELECT DISTINCT ON (object_id)
object_id, event_timestamp ---, more columns
FROM test_select
ORDER BY object_id, event_timestamp DESC
) AS t
ORDER BY event_timestamp DESC ;
Като алтернатива можете да използвате прозоречни функции, като ROW_NUMBER()
:
WITH cte AS
( SELECT ROW_NUMBER() OVER (PARTITION BY object_id
ORDER BY event_timestamp DESC)
AS rn,
object_id, event_timestamp ---, more columns
FROM test_select
)
SELECT object_id, event_timestamp ---, more columns
FROM cte
WHERE rn = 1
ORDER BY event_timestamp DESC ;
или агрегат MAX()
с OVER
:
WITH cte AS
( SELECT MAX(event_timestamp) OVER (PARTITION BY object_id)
AS max_event_timestamp,
object_id, event_timestamp ---, more columns
FROM test_select
)
SELECT object_id, event_timestamp ---, more columns
FROM cte
WHERE event_timestamp = max_event_timestamp
ORDER BY event_timestamp DESC ;