不能添加或更新子行，外键约束失败

Question

我有一个表

1.

CREATE TABLE `Parent` (
`ID` bigint(19) NOT NULL DEFAULT '0', 
PRIMARY KEY (`ID`), 
) ENGINE=InnoDB DEFAULT CHARSET=utf8; 

2.

CREATE TABLE `Child_1` (
`ParentID` bigint(19) NOT NULL DEFAULT '0', 
`ID` bigint(19) NOT NULL DEFAULT '0', 
PRIMARY KEY (`ParentID`,`ID`), 
KEY `Child_1_FK1_IDX` (`ParentID`,`ID`), 
CONSTRAINT `Child_1_FK1` FOREIGN KEY (`ParentID`, `ID`) REFERENCES `Child_2` (`ParentID`, `ID`) ON DELETE CASCADE 
) ENGINE=InnoDB DEFAULT CHARSET=utf8; 

3.

CREATE TABLE `Child_2` (
`ParentID` bigint(19) NOT NULL DEFAULT '0', 
`ID` bigint(19) NOT NULL DEFAULT '0', 
PRIMARY KEY (`ParentID`,`ID`), 
KEY `Child_2_FK1_IDX` (`ParentID`), 
CONSTRAINT `Child_2_FK1` FOREIGN KEY (`ParentID`) REFERENCES `Parent` (`ParentID`) ON DELETE CASCADE 
) ENGINE=InnoDB DEFAULT CHARSET=utf8; 

不幸的是，我已经删除了第二个表约束。

CONSTRAINT `Child_1_FK1` FOREIGN KEY (`ParentID`, `ID`) REFERENCES `Child_2` (`ParentID`, `ID`) ON DELETE CASCADE 

我该如何恢复？

Answer 1

这是更好地采取倾倒。冷启动数据库。

Answer 2

试试这个（未测试）：

ALTER TABLE Child_1 
ADD FOREIGN KEY (`ParentID`, `ID`) 
REFERENCES `Child_2` (`ParentID`, `ID`) 
ON DELETE CASCADE 

更新：

为了得到记录违反约束，运行此：

select child1.ID from 
    Child_1 child1 left join Child_2 child2 on child1.ParentID=child2.ParentID and child1.ID=child2.ID 
where child2.ID is null and child2.ParentID is null;