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我四处寻找适合我正在寻找的东西。我绝不接近 SQL 专家，所以我在这里问。无论 c 是否存在，我都想抓住 a 和 b，但如果 c 确实存在，则将其加入返回。这是我目前正在使用的声明：

SELECT a.display_name, a.first_name, a.last_name, a.profile_image, a.tagline,
       a.bragging_rights, a.about_me, b.type AS post_type, b.title AS post_title,
       b.published AS post_published, b.updated AS post_updated,
       b.content AS post_content, b.num_replies AS post_replies, 
       b.num_plus_ones AS post_plus_ones, b.num_reshares AS post_reshares,
       c.display_name AS attach_display_name, c.content AS attach_content,
       c.url AS attach_url, c.image_url AS attach_image,
       c.image_width AS attach_width, c.image_height AS attach_height,
       c.full_image_url AS attach_full_image
  FROM cr_google_profiles a
  JOIN cr_google_posts b
  LEFT JOIN cr_google_post_attachements c 
    ON b.post_id = c.post_id
 WHERE a.google_id = :google_id AND b.google_id = :google_id AND c.google_id = :google_id

我真的不知道如何做到这一点；我一直在 YouTubing 并阅读手册，但没有想出任何可以完成我正在寻找的东西。任何帮助或建设性的批评都非常受欢迎。

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2 回答 2

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您是否正在寻找一种正确使用JOIN表格的方法？像这样的东西

SELECT ...
  FROM cr_google_profiles a JOIN cr_google_posts b 
    ON a.google_id = b.google_id LEFT JOIN cr_google_post_attachements c 
    ON b.google_id = c.google_id AND b.post_id = c.post_id 
WHERE a.google_id = :google_id
于 2013-06-16T03:26:44.130 回答
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我认为您的问题是您没有为aand的连接指定连接条件b，因此您确实需要类似的东西：

SELECT a.display_name, a.first_name, a.last_name, a.profile_image, a.tagline,
       a.bragging_rights, a.about_me, b.type AS post_type, b.title AS post_title,
       b.published AS post_published, b.updated AS post_updated,
       b.content AS post_content, b.num_replies AS post_replies, 
       b.num_plus_ones AS post_plus_ones, b.num_reshares AS post_reshares,
       c.display_name AS attach_display_name, c.content AS attach_content,
       c.url AS attach_url, c.image_url AS attach_image,
       c.image_width AS attach_width, c.image_height AS attach_height,
       c.full_image_url AS attach_full_image
  FROM cr_google_profiles a
  JOIN cr_google_posts b
    ON a.google_id = b.google_id
  LEFT JOIN cr_google_post_attachements c 
    ON b.post_id = c.post_id
 WHERE a.google_id = :google_id
   AND b.google_id = :google_id
   AND c.google_id = :google_id
于 2013-06-16T03:28:09.380 回答