mysql - 选择具有 dup 值的最近项目

Question

鉴于以下信息，我如何在唯一的 params 和 cron_action_id 对上选择最新的订单项(基于 time_entered)还没被处决吗？

cron_schedule

例如，id 1、2和4具有相同的params和cron_action_id，所以我不需要选择所有3，只需选择id 4。id的原理相同3/5 和 7/8。

我只能做到这一点

SELECT *
FROM cron_schedule cs
INNER JOIN cron_actions ca
ON cs.cron_action_id = ca.cron_action_id
WHERE time_executed = 0
-- GROUP BY (params, cron_action_id) ?

这应该返回 id 为 4、5、6 和 8 的行

谢谢

Answer 1

SELECT t1.* 
FROM   cron_schedule t1 
  INNER JOIN (SELECT params, 
    cs.cron_action_id, 
    Max(time_entered) AS time_entered 
    FROM cron_schedule cs 
    INNER JOIN cron_actions ca 
    ON cs.cron_action_id = ca.cron_action_id 
    WHERE  time_executed = 0 
    GROUP  BY params, cron_action_id) AS t2 
  ON t1.params = t2.params 
    AND t1.cron_action_id = t2.cron_action_id 
    AND t1.time_entered = t2.time_entered 
  INNER JOIN cron_actions ca2 
  ON t1.cron_action_id = ca2.cron_action_id 
  WHERE  t1.time_executed = 0