För att kunna välja alla kolumner och inte bara object_id
och MAX(event_timestamp)
, kan du använda DISTINCT ON
SELECT DISTINCT ON (object_id)
object_id, event_timestamp ---, more columns
FROM test_select
ORDER BY object_id, event_timestamp DESC ;
Om du vill ha resultaten sorterade efter event_timestamp DESC
och inte av object_id
måste du inkludera det i en härledd tabell 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 använda fönsterfunktioner, som 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 samla 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 ;