＃1222-使用的SELECT语句的列数不同

金毛球宝宝

为什么我得到＃1222-使用的SELECT语句具有不同数量的列？我正在尝试从此用户朋友和他自己处加载墙贴。
SELECT u.id AS pid, b2.id AS id, b2.message AS message, b2.date AS date FROM
(
(
      SELECT b.id AS id, b.pid AS pid, b.message AS message, b.date AS date FROM
      wall_posts AS b
      JOIN Friends AS f ON f.id = b.pid
      WHERE f.buddy_id = '1' AND f.status = 'b'
      ORDER BY date DESC
      LIMIT 0, 10
)
UNION
(
      SELECT * FROM
      wall_posts
      WHERE pid = '1'
      ORDER BY date DESC
      LIMIT 0, 10
)
ORDER BY date DESC
LIMIT 0, 10
) AS b2
JOIN Users AS u
ON b2.pid = u.id
WHERE u.banned='0' AND u.email_activated='1'
ORDER BY date DESC
LIMIT 0, 10
wall_posts表结构如下所示 id date privacy pid uid message
Friends表结构如下所示 Fid id buddy_id invite_up_date status
pid代表配置文件ID。我不太确定发生了什么。

解决方案:


            UNION中的第一条语句返回四列：
SELECT b.id AS id,
   b.pid AS pid,
   b.message AS message,
   b.date AS date
  FROM wall_posts AS b
第二个返回六，因为*扩展为包括以下所有列WALL_POSTS：
SELECT b.id,
   b.date,
   b.privacy,
   b.pid.
   b.uid message
  FROM wall_posts AS b
在UNION与UNION ALL运营商要求：
[ol]组成UNION查询的所有语句中存在相同数量的列
数据类型必须在每个位置/列都匹配
[/ol]
使用：
FROM ((SELECT b.id AS id,
         b.pid AS pid,
         b.message AS message,
         b.date AS date
      FROM wall_posts AS b
      JOIN Friends AS f ON f.id = b.pid
   WHERE f.buddy_id = '1' AND f.status = 'b'
ORDER BY date DESC
   LIMIT 0, 10)
   UNION
   (SELECT id,
            pid,
            message,
            date
      FROM wall_posts
      WHERE pid = '1'
   ORDER BY date DESC
      LIMIT 0, 10))

＃1222-使用的SELECT语句的列数不同

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