Question

我正在为我的Wordpress博客构建一个“作者”页面，其中列出了所有当前的网站贡献者以及其他各种信息，例如他们发布的帖子数量，上次发布的日期等等。

谷歌和Wordpress Codex已经指出我要在MySQL中使用子查询来在一个查询中提取我需要的所有数据，并且它非常适合获取每位作者发布的帖子数量。

我无法工作的是为每位作者查找最新帖子的帖子ID。

当前查询有效，没有最新帖子：

SELECT users.ID, (SELECT count(*) FROM posts, users WHERE users.ID = posts.post_author AND posts.post_type = 'post' AND posts.post_status = 'publish') AS post_count FROM users ORDER BY post_count DESC

我尝试获取每位作者的最新帖子ID（'latest_post_ID'）：

SELECT users.ID, (SELECT count(*) FROM posts, users WHERE users.ID = posts.post_author AND posts.post_type = 'post' AND posts.post_status = 'publish') AS post_count, (SELECT posts.ID FROM posts, users WHERE users.ID = posts.post_author AND posts.post_type = 'post' AND posts.post_status = 'publish' ORDER BY posts.post_date DESC LIMIT 1) AS latest_post_ID FROM users ORDER BY post_count DESC

添加子查询存在问题 - 查询将查找与任何作者匹配的任何发布帖子，而不是我想要的帖子（'users.ID = posts.post_author'）。

如果有人使用SQL-fu可以指出我在滥用和/或滥用MySQL子查询的地方，我会非常感激。

Answer 1

  SELECT u.id,
         COUNT(*) AS post_count,
         MAX(p.id) AS latest_post_id
    FROM POSTS p
    JOIN USERS u ON u.ID = p.post_author 
   WHERE p.post_type = 'post' 
     AND p.post_status = 'publish'
GROUP BY u.id
ORDER BY post_count DESC

我不建议在SELECT子句中使用SELECTS。虽然它们有效，但它们会提供最差的性能。

Answer 2

试试这个。

SELECT a.ID, 

(SELECT count(*) 
FROM posts 
WHERE a.ID = posts.post_author 
AND posts.post_type = 'post' 
AND posts.post_status = 'publish') AS post_count, 

(SELECT posts.ID 
FROM posts 
WHERE a.ID = posts.post_author 
AND posts.post_type = 'post' 
AND posts.post_status = 'publish' 
ORDER BY posts.post_date DESC LIMIT 1) AS latest_post_ID 

FROM users As a 
ORDER BY post_count DESC

Answer 3

以下查询应该在MySQL中有效：

SELECT posts.ID FROM posts,
(SELECT MAX(posts.post_date) AS max_date,
posts.post_author AS author

FROM posts 

WHERE users.ID = posts.post_author 

GROUP BY posts.post_author) AS max_date_table

WHERE posts.post_date = max_date_table.max_date AND
posts.post_author = max_date_table.author

通过作者查找最新帖子

3 个答案: