MySQL錯誤＃1452嘗試添加約束

Question

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Error appears in sql when trying to add multiple foreign keys

我試圖改變一個表，這樣我可以在MySQL數據庫中添加一個外鍵約束時出現：

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

問題是，它是給我這個錯誤：

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)

是什麼錯誤實際上意味着，什麼是可能的解決辦法可能我爲了解決這一問題進行？

Answer 1

也許Image_Question.QuestionId不是唯一的。而且它看起來像FK應該走相反的路，從Image_Question到Question