Get the latest row of data

Question

table: task: id (bigint) name (varchar). Save task details job: id(varchar(UUID))task_id(bigint(class ID)),staus>(varchar(50)),created_time(timestamp). The possible values ​​for saving the task execution details status are FAIL/COMPLETED/INTERRUPTED What I want to achieve is to get all the latest values ​​for each task from the jobs table. If the job does not exist in the task, the return status is

P粉755863750 · Answer

For SQL versions that support ROW_NUMBER(), you can do this:

WITH info as(
  SELECT
    p.id, 
    j.status,
    ROW_NUMBER() OVER(PARTITION BY p.id ORDER BY j.created_time DESC) AS rn
  FROM tas p
  LEFT JOIN job j ON j.task_id = p.id
)
SELECT id, status
FROM info
WHERE rn = 1

Otherwise, just use cte or subquery.

SELECT p.id, t.status
FROM tas AS p
LEFT JOIN (
  SELECT task_id, MAX(created_time) as created_time
  FROM job
  GROUP BY task_id
) as lt
ON p.id = lt.task_id
LEFT JOIN task AS t ON lt.task_id = t.task_id AND lt.created_time = t.created_time

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