'on子句'中的MySQL未知列:(

Question

我的查询看起来像

SELECT а.*, m.username, m.picture, m.picture_active
FROM questions_answer AS а 
INNER JOIN members AS m ON а.poster_id=m.member_id
INNER JOIN questions AS q ON q.question_id=a.question_id
ORDER BY a.postdate DESC

我收到错误消息：

Unknown column 'a.question_id' in 'on clause'

我不知道怎么了，请帮我解决这个问题。

表questions是

CREATE TABLE IF NOT EXISTS `questions` (
  `question_id` int(9) unsigned NOT NULL AUTO_INCREMENT,
  `member_id` int(9) unsigned NOT NULL DEFAULT '0',
  `question` text NOT NULL,
  `postdate` int(10) unsigned NOT NULL DEFAULT '0',
  `active` tinyint(1) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`question_id`),
  KEY `member_id` (`member_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

和questions_answer是

CREATE TABLE IF NOT EXISTS `questions_answer` (
  `answer_id` bigint(12) unsigned NOT NULL AUTO_INCREMENT,
  `question_id` int(9) unsigned NOT NULL,
  `poster_id` int(9) unsigned NOT NULL,
  `body` text NOT NULL,
  `postdate` int(9) unsigned NOT NULL,
  PRIMARY KEY (`answer_id`),
  KEY `question_id` (`question_id`),
  KEY `poster_id` (`poster_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

Answer 1

您的表questions_answer可能没有列question_id

Answer 2

似乎您没有a.question_id列

检查该表的结构。

Answer 3

没有任何叫列question_id在questions_answer表。

Answer 4

有趣的是，如果我使用此代码，它将起作用：

SELECT qa.*
FROM questions_answer qa
INNER JOIN questions q ON qa.question_id = q.question_id
ORDER BY qa.postdate DESC

SQL提琴

因此，要将其应用于您的查询：

SELECT qa.*, m.username, m.picture, m.picture_active
FROM questions_answer qa
INNER JOIN questions q ON qa.question_id = q.question_id
INNER JOIN members m ON qa.poster_id = m.member_id
ORDER BY qa.postdate DESC

Answer 5

您的questions_answer表别名a存在一些问题。 这很可能不是字母a 。

FROM questions_answer AS а 

我在玩弄它，发现一个错误，提示“ Unknown table 'аa':如您所见，它可能是一个特殊字符。 网上的简短搜索结果是字母Eth

我用字符a替换了alias ，查询工作正常。

SELECT a.*, m.username, m.picture, m.picture_active
FROM questions_answer AS a
INNER JOIN members AS m ON a.poster_id=m.member_id
INNER JOIN questions AS q ON q.question_id=a.question_id
ORDER BY a.postdate DESC

在此处查看示例，只需将查询复制粘贴到此处并尝试运行，由于alias字符问题，它将抱怨。 从你行，并更换所有你甚至可以复制别名a与它S，它也能发挥作用。