Question

我正在回答这个问题的答案： MySQL: is it possible to group_concat multiple rows?

但是我遇到了MySql错误：

#1054 - Unknown column 'CM_Cocktail.id' in 'field list'。

当我删除此CM_Cocktail.id时，会出现下一个错误：#1054 - Unknown column 'CM_Zutat.name' in 'field list'。我试图使用别名，但它变得更糟......也许我是盲人。

＆＃13;

SELECT 
  CM_Cocktail.id, CM_Cocktail.name,
  GROUP_CONCAT(CM_Zutat.name SEPARATOR ', ')
FROM (
  SELECT CM_Cocktail.id, CM_Cocktail.name AS cname, CM_Zutat.name
              FROM CM_Cocktail, CM_CocktailHatZutat, CM_Zutat
              WHERE CM_Cocktail.id=CM_CocktailHatZutat.cocktail_id
              AND CM_CocktailHatZutat.zutat_id=CM_Zutat.id
) group_attr
GROUP BY CM_Cocktail.id;

＆＃13;

CREATE TABLE IF NOT EXISTS `CM_Cocktail` (
  `id` int(3) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

＆＃13;

CREATE TABLE IF NOT EXISTS `CM_CocktailHatZutat` (
  `cocktail_id` int(3) NOT NULL,
  `zutat_id` int(3) NOT NULL,
  `zutat_menge` int(4) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

＆＃13;

CREATE TABLE IF NOT EXISTS `CM_Zutat` (
  `id` int(3) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;

＆＃13;

Answer 1

您需要在子查询中定义列别名，而不是将别名用作父字段，如下例所示：

SELECT 
CocktailID, cname,
GROUP_CONCAT(ZName SEPARATOR ', ')
FROM (
SELECT CM_Cocktail.id as CocktailID, CM_Cocktail.name AS cname, CM_Zutat.name as ZName
     FROM CM_Cocktail, CM_CocktailHatZutat, CM_Zutat
     WHERE CM_Cocktail.id=CM_CocktailHatZutat.cocktail_id
     AND CM_CocktailHatZutat.zutat_id=CM_Zutat.id
) group_attr
GROUP BY CocktailID;

Answer 2

试试这个

SELECT 
id, name,
GROUP_CONCAT(CM_Zutat.name SEPARATOR ', ')
FROM (
SELECT CM_Cocktail.id, CM_Cocktail.name AS cname, CM_Zutat.name
          FROM CM_Cocktail, CM_CocktailHatZutat, CM_Zutat
          WHERE CM_Cocktail.id=CM_CocktailHatZutat.cocktail_id
          AND CM_CocktailHatZutat.zutat_id=CM_Zutat.id
) group_attr
GROUP BY id;

因为您使用子查询

MySql：＆＃39;字段列表中的未知列ID＆＃39;

2 个答案: