php - 我如何构造这种sql查询

Question

我有下面的数据库表

我想向带有 owner_id 的用户显示通知 1. 通知显示告诉所有者有两个用户(ID 为 17 和 2)用 post_id< 评论了他/她的帖子 1。 我尝试过以下查询，但它返回 2 行。我如何构建查询以返回一行，因为我希望一起返回一篇文章的通知？谢谢。

SELECT DISTINCT commenters_id, id, owner_id, 
                post_id, type, UNIX_TIMESTAMP(date_done) AS date 
FROM notification 
GROUP BY commenters_id 
HAVING owner_id = '$user_id' AND commenters_id != '$user_id' 
ORDER BY date_done DESC

Answer 1

此代码不会为您提供commenters_id，而是会统计每个帖子的回复人数。 日期将是某人最后一次回复该特定帖子的时间:

SELECT
    COUNT(DISTINCT commenters_id) AS commenter_count,
    owner_id,
    post_id,
    type,
    UNIX_TIMESTAMP(MAX(date_done)) AS date 
FROM notification
WHERE owner_id = '$user_id' AND commenters_id != '$user_id' 
GROUP BY owner_id, post_id, type
ORDER BY UNIX_TIMESTAMP(MAX(date_done)) DESC