For at kunne vælge alle kolonner og ikke kun object_id
og MAX(event_timestamp)
, kan du bruge DISTINCT ON
SELECT DISTINCT ON (object_id)
object_id, event_timestamp ---, more columns
FROM test_select
ORDER BY object_id, event_timestamp DESC ;
Hvis du vil have resultaterne sorteret efter event_timestamp DESC
og ikke af object_id
, skal du inkludere det i en afledt tabel eller en 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 ;
Alternativt kan du bruge vinduesfunktioner, såsom 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 ;
eller samle MAX()
med 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 ;