子查询中的Mysql最大日期

Question

我不知道如何让这个子查询工作以获取该行的最新日期。

SELECT Thread_Heading.*, Thread_Articles.*, Thread_ArticlesPost.* 
FROM Thread_Heading 
LEFT JOIN Thread_Articles 
    ON Thread_Articles.Thread_Article_Head_id=Thread_Heading.Thread_Head_id 
LEFT JOIN 
(
    SELECT Thread_ArticlesPost.* 
    FROM Thread_ArticlesPost 
    ORDER BY Thread_ArticlePost_DT DESC
) Thread_ArticlesPost 
    ON  Thread_ArticlesPost.Thread_ArticlePost_Article_id=Thread_Articles.Thread_Article_id  
WHERE Thread_Head_Level = '5' 
GROUP BY Thread_Heading.Thread_Head_id 
ORDER BY Thread_ArticlePost_DT DESC

我需要按每篇主题文章的最新帖子来排序文章发布日期。 对 sql 和 php 相当陌生，我只是无法解决这个问题，我们将不胜感激。

T

ABLE: Thread_Heading | 
Thread_Head_id
Thread_Head_Name
Thread_Head_Type
Thread_Head_Creator
Thread_Head_Date
Thread_Head_Level

TABLE: Thread_Articles | 
Thread_Article_id
Thread_Article_Head_id
Thread_Article_Creator
Thread_Article_DT
Thread_Article_Level
Thread_Article_Type
Thread_Article_Title

TABLE: Thread_ArticlesPost | 
Thread_ArticlePost_id
Thread_ArticlePost_Head_id
Thread_ArticlePost_Article_id
Thread_ArticlePost_Creator
Thread_ArticlePost_DT
Thread_ArticlePost_Level
Thread_ArticlePost_Type
Thread_ArticlePost_Title
Thread_ArticlePost_Content

我需要像这样显示日期:

Head Name | Article title | ORDER BY LATEST ArticlePost DT | ArticlePost Creator

我使用左连接的原因是即使没有文章或文章回复也能获取左数据。

感谢您的帮助。

感谢 Blue 用它来显示数据

选择*
来自
( SELECT th.Thread_Head_Name,
ta., tp1.maxdate, tp2. FROM Thread_Heading 日 LEFT JOIN Thread_Articles ta ON th.Thread_Head_id = ta.Thread_Article_Head_id 左连接
( 选择最大(Thread_ArticlePost_DT)最大日期，
Thread_ArticlesPost.* 来自 Thread_ArticlesPost 按 T​​hread_ArticlePost_Article_id 分组 ) tp1 ON tp1.Thread_ArticlePost_Article_id=ta.Thread_Article_id
左加入 Thread_ArticlesPost tp2 ON tp1.Thread_ArticlePost_Article_id = tp2.Thread_ArticlePost_Article_id AND tp1.maxdate = tp2.Thread_ArticlePost_DT
WHERE th.Thread_Head_Level = '5' ORDER BY tp1.maxdate DESC) m 按 T​​hread_Head_Name 分组 按 T​​hread_ArticlePost_DT DESC 排序

Answer 1

在没有看到完整的表模式的情况下，您会想要做类似这样的事情:

SELECT th.*, ta.*, tp.* 
FROM Thread_Heading th
LEFT JOIN Thread_Articles ta
    ON th.Thread_Head_id = ta.Thread_Article_Head_id
LEFT JOIN 
(
    SELECT max(Thread_ArticlePost_DT) maxDate, Thread_ArticlesPost.* 
    FROM Thread_ArticlesPost 
    GROUP BY Thread_ArticlePost_Article_id
) Thread_ArticlesPost tp
    ON  tp.Thread_ArticlePost_Article_id=ta.Thread_Article_id  
WHERE Thread_Head_Level = '5' 
GROUP BY th.Thread_Head_id 
ORDER BY tp.maxdate DESC

根据您的编辑，以下应返回您想要的数据:

SELECT th.Thread_Head_Name, 
  ta.Thread_Article_Title,
  tp1.maxdate,
  tp2.Thread_ArticlePost_Creator
FROM Thread_Heading th
LEFT JOIN Thread_Articles ta
    ON th.Thread_Head_id = ta.Thread_Article_Head_id
LEFT JOIN 
(
    SELECT max(Thread_ArticlePost_DT) maxDate, 
      Thread_ArticlesPost.Thread_ArticlePost_Article_id
    FROM Thread_ArticlesPost 
    GROUP BY Thread_ArticlePost_Article_id
) tp1
  ON  tp1.Thread_ArticlePost_Article_id=ta.Thread_Article_id  
LEFT JOIN Thread_ArticlesPost tp2
  ON tp1.Thread_ArticlePost_Article_id = tp2.Thread_ArticlePost_Article_id
  AND tp1.maxdate = tp2.Thread_ArticlePost_DT 
WHERE th.Thread_Head_Level = '5' 
ORDER BY tp1.maxdate DESC

编辑 #2，根据您的评论，我认为以下查询应该可以解决所有遗留问题:

SELECT th.Thread_Head_id,
  th.Thread_Head_Name,
  ta.Thread_Article_Title,
  tp.Thread_ArticlePost_Creator,
  tap.MaxPostDate
FROM Thread_Heading th 
LEFT JOIN
(
  SELECT max(ta.Thread_Article_DT) MaxArticleDate, 
    ta.Thread_Article_Head_id,
    max(tp.Thread_ArticlePost_DT) MaxPostDate
  FROM Thread_Articles ta
  LEFT JOIN Thread_ArticlesPost tp
    ON ta.Thread_Article_id = tp.Thread_ArticlePost_Article_id
  GROUP BY Thread_Article_Head_id
) tap
  ON th.Thread_Head_id = tap.Thread_Article_Head_id 
LEFT JOIN Thread_Articles ta
  ON tap.Thread_Article_Head_id = ta.Thread_Article_Head_id
  AND tap.MaxArticleDate = ta.Thread_Article_DT
LEFT JOIN Thread_ArticlesPost tp
  ON tap.MaxPostDate = tp.Thread_ArticlePost_DT
WHERE th.Thread_Head_Level = '5'
ORDER BY MaxPostDate desc

参见 SQL Fiddle With Demo