Question

我有一张表格，其中多次使用subscription_id，每个月客户都会收取相同数据生成的订单。唯一的订单ID，所以有一个'updated_at'列也会更新，所以我想从基于subscription_id的表中获得一（1）条最新记录，我使用的是以下查询，但它不起作用并获得旧记录。

SELECT *
FROM members_subscriptions
WHERE status = 'active'
GROUP BY subscription_id
ORDER BY updated_at DESC

任何人都可以告诉我这个查询有什么问题......

Answer 1

您需要获取MAX()的{{1}}，按分组运行排序，以便与最新日期进行比较

updated_at

或

SELECT DISTINCT *
FROM members_subscriptions
WHERE status = 'active'
AND updated_at IN(
SELECT MAX(updated_at) 
FROM members_subscriptions 
GROUP BY subscription_id
)
ORDER BY updated_at DESC

Answer 2

假设每个子信息在updated_at中只能包含唯一日期，那么此查询应该会给出所需的结果：

SELECT *
FROM members_subscriptions
WHERE status = 'active'
AND (subscription_id, updated_at) IN(
    SELECT subscription_id, MAX(updated_at) 
    FROM members_subscriptions 
    GROUP BY subscription_id
)
ORDER BY updated_at DESC

但是，如果一个订阅的日期可能相同，那么查询必须使用唯一的id来获取两个或更多相同日期的一条记录：

SELECT *
FROM members_subscriptions m
WHERE status = 'active'
  AND id = (
      SELECT id FROM members_subscriptions m1
      WHERE m.subscription_id = m1.subscription_id
        AND status = 'active'
      ORDER BY updated_at DESC
      LIMIT 1
)

Answer 3

您的查询存在的问题是，首先对结果进行分组，然后才对其进行排序。如果您需要最新结果，则需要执行以下操作：

SELECT *
   FROM members_subscriptions as main
   WHERE status = `active` AND `updated_at` = (
       SELECT MAX(`updated_at`) FROM members_subscriptions as sub
       WHERE status='active' and main.`subscription_id` = sub.`subscription_id`
   )

Answer 4

SELECT distinct (name)
FROM members_subscriptions
WHERE status = 'active'
GROUP BY subscription_id
ORDER BY updated_at DESC

对您要查找的字段名称使用distinct

如何根据mysql中的一列获取唯一记录

4 个答案: