MySQL错误＃1452尝试添加约束

Question

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Error appears in sql when trying to add multiple foreign keys

我试图改变一个表，这样我可以在MySQL数据库中添加一个外键约束时出现：

ALTER TABLE `Question` ADD CONSTRAINT `FK_question` FOREIGN KEY (`QuestionId`) 
REFERENCES `Image_Question` (`QuestionId`) ON DELETE CASCADE ; 

问题是，它是给我这个错误：

1452 - Cannot add or update a child row: a foreign key constraint fails ( mobile_app .

'#sql-4517_15241'>, CONSTRAINT FK_question FOREIGN KEY (QuestionId) REFERENCES Image_Question (QuestionId) ON DELETE CASCADE)

是什么错误实际上意味着，什么是可能的解决办法可能我为了解决这一问题进行？

Answer 1

也许Image_Question.QuestionId不是唯一的。而且它看起来像FK应该走相反的路，从Image_Question到Question