Re: error 1452 "cannot add or update a child row: foreign key constaint fails"

[Mostafa Othman]

Hi,
I had the same problem but it was solved as follows:
1-Before assigning a table column as Foreign key, you should MAKE SURE that it contains at least on VALID data, I mean a VALID values in the table column which it will reference to.
On the other hand, if it is empty column you won't face any problem, as the problem arise when it contains no data related to the column which it will point to.

Example:
table: exam
id = 1;
no_question=20;

table:question (had a foreign key (exam.id) that references to exam.id)
ques.id = 1;
exam_id: 1 (it should contains at least ONE VALID data in column (exam.id), such as 1) -----> exam.id

for more information have a look at following link:

http://myownthesis.blogspot.com/2007/10/foreign-key-in-mysql-error-1452-and.html

Thanks.



Edited 1 time(s). Last edit at 07/31/2008 06:16AM by Mostafa Othman.