Question

我需要从我的数据库中分页帖子，我写下一个查询：

SELECT posts.ID, posts.date, comments.name, comments.value 
FROM posts 
INNER JOIN comments 
    ON comments.ID = posts.ID 
INNER JOIN relations 
    ON relations.ID = posts.ID 
WHERE type_rel=1 AND status_post=1 AND 
LIMIT 0,10

问题出在LIMIT句子中，我只需要限制“帖子”表。

评论表有很多行，如果我把限制放在“0,10”中，“posts”表限制为10个帖子，但评论表也限制为10个。

有人能解决我的问题吗？我在PHP查询中使用它。

抱歉我的英语不好，提前谢谢。

Answer 1

您可以使用子查询来限制结果集，然后加入：

SELECT 
  posts.ID, 
  posts.date, 
  comments.name, 
  comments.value 
FROM
  (SELECT * FROM posts WHERE status_post = 1 LIMIT 0,10) posts
LEFT JOIN 
  comments 
  ON comments.ID = posts.ID 
LEFT JOIN 
  relations 
  ON relations.ID = posts.ID AND relations.type_rel = 1

从评论中，索引文件中的查询是错误的，这是正确的：

SELECT 
  wp_posts.ID, 
  wp_posts.post_date, 
  wp_postmeta.meta_key, 
  wp_postmeta.meta_value 
FROM (SELECT * FROM wp_posts WHERE post_status="publish" AND post_type="post" LIMIT 0,2) wp_posts 
LEFT JOIN wp_postmeta 
  ON wp_postmeta.post_id = wp_posts.ID 
LEFT JOIN wp_term_relationships 
  ON wp_term_relationships.object_id = wp_posts.ID 
  AND wp_term_relationships.term_taxonomy_id=2

示例结果here，你可以看到你有两个帖子，id 1和5。

如果您想保留term_taxonomy_id = 2使用此帖子的帖子：

SELECT 
  wp_posts.ID, 
  wp_posts.post_date, 
  wp_postmeta.meta_key, 
  wp_postmeta.meta_value 
FROM (
  SELECT * 
  FROM wp_posts 
  JOIN wp_term_relationships 
  ON wp_term_relationships.object_id = wp_posts.ID 
  AND wp_term_relationships.term_taxonomy_id = 2
  WHERE post_status="publish" AND post_type="post" LIMIT 0,2) wp_posts 
LEFT JOIN wp_postmeta ON wp_postmeta.post_id = wp_posts.ID

Example here，帖子ID为5和7，限制0,1仅返回5.

Answer 2

您只能限制从posts表返回的行

SELECT posts.ID, posts.date, comments.name, comments.value 
FROM (select * from posts limit 0,10) posts
INNER JOIN comments 
    ON comments.ID = posts.ID 
INNER JOIN relations 
    ON relations.ID = posts.ID 
WHERE type_rel=1 AND status_post=1

Answer 3

您可以尝试：

SELECT a.ID, a.date, a.name, a.value
FROM (
SELECT posts.ID, posts.date, comments.name, comments.value,
       @post_rank := IF(@current_post = posts.ID, @post_rank + 1, 1) AS post_rank,
   @current_post := posts.ID
FROM posts 
INNER JOIN comments 
    ON comments.ID = posts.ID 
INNER JOIN relations 
    ON relations.ID = posts.ID 
WHERE type_rel=1 AND status_post=1
ORDER BY posts.ID DESC )a
WHERE a.post_rank <= 10

MySQL选择内部加入，仅限首先限制

3 个答案: