query.sql

SELECT "api_thread"."id",
       "api_thread"."conference_id",
       "api_thread"."title",
       "api_thread"."description",
       "api_thread"."is_closed",
       "api_thread"."is_pinned",
       "api_thread"."post_moderation_allowed",
       "api_thread"."has_voting",
       "api_thread"."created_at",
       "api_thread"."expired",
       "api_thread"."owner_id",
       "api_thread"."sv",
       (SELECT U0."clear_content"
        FROM "api_post" U0
        WHERE U0."thread_id" = ("api_thread"."id")
        ORDER BY U0."created" DESC
        LIMIT 1) AS "last_post"
FROM "api_thread"


SELECT at.*, ap.*
FROM api_thread at
         LEFT JOIN api_post ap ON at.id = ap.thread_id
WHERE ap.created IN (SELECT max(created)
                     FROM api_thread at
                              LEFT JOIN api_post ap ON at.id = ap.thread_id
                     GROUP BY at)