Question

您好，他的查询给了我以下错误：

'on clause'

中的未知列'm.home_team_id'

SELECT DISTINCT (
`m`.`match_id`), 
`m`.`competition_id`, 
`m`.`date`, 
`h`.`team_name` AS "homeTeam", `h`.`team_id` AS "homeTeamID", 
`a`.`team_name` AS "awayTeam", `a`.`team_id` AS "awayTeamID", 
`o`.`for`, `o`.`against` 
FROM `single` bs, `matches` m, `teams` t, `outcomes` o 
JOIN `teams` `h` ON `m`.`home_team_id`=`h`.`team_id` 
JOIN `teams` `a` ON `m`.`away_team_id`=`a`.`team_id` 
WHERE `bs`.`match_id`=`m`.`match_id` 
AND `m`.`score_id`=`o`.`outcome_id` 
AND `actual_return` IS NOT NULL`enter code here`

m是名为匹配的表的别名，其中包含home_team_id列和away_team_id列，因此我无法确定无法找到列的原因？

艾伦。

Answer 1

SELECT 
     DISTINCT (`m`.`match_id`), 
      `m`.`competition_id`, 
      `m`.`date`, 

      `h`.`team_name` AS "homeTeam",
      `h`.`team_id` AS "homeTeamID", 

      `a`.`team_name` AS "awayTeam",
      `a`.`team_id` AS "awayTeamID", 

      `o`.`for`, 
      `o`.`against` 

FROM `single` bs

      join `matches` m ON bs.match_id = m.match_id
      join `outcomes` o m.score_id = o.outcome_id 
      join `teams` t   --<--- I don't know what the join is for `teams` here 
                          --- you probably don't need this in the query at all 

      JOIN `teams` `h` ON `m`.`home_team_id`=`h`.`team_id` 
      JOIN `teams` `a` ON `m`.`away_team_id`=`a`.`team_id` 

WHERE  `actual_return` IS NOT NULL

Answer 2

FROM a, b, c
JOIN d ON ...
JOIN e ON ...

逻辑上的工作方式如下：

FROM a, b,
  (c
   JOIN d ON ...
   JOIN e ON ...)

因为JOIN关键字的优先级高于逗号。

因此，对于您的示例，当它尝试执行JOIN时，它不知道m是什么。

因此，您应该能够通过将matches置于最后，即更改

来解决此问题

FROM `single` bs, `matches` m, `teams` t, `outcomes` o

为：

FROM `single` bs, `teams` t, `outcomes` o, `matches` m

但是，正如迈克尔建议的那样，你不应该混合使用显式连接（使用JOIN）和隐式连接（使用逗号）。

此外，似乎根本没有使用teams t。

Answer 3

我猜你的错误在于放置JOINS的位置。如果您想加入表格m，则应将JOIN放在旁边，而不是表o旁边。

我认为现在的方式是，该语句试图将表o与表h连接起来。这就是为什么它找不到表（和列）m。

无法找到MySQL列

3 个答案: