gistfile1.sql

SELECT task_events.task_id, task_events.state 
FROM tasks 
INNER JOIN task_events ON task_events.task_id = tasks.id 
WHERE task_events.created_at = 
  (SELECT MAX(task_events.created_at) FROM task_events WHERE task_events.task_id = tasks.id)
GROUP BY tasks.id, task_events.id 
ORDER by tasks.id ;



SELECT DISTINCT ON (task_id)
    task_id, state 
FROM task_events 
ORDER by task_id, created_at DESC ;