Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails

Question

I\'m having a bit of a strange problem. I\'m trying to add a foreign key to one table that references another, but it is failing for some reason. With my limited knowledge o

Answer 1

It seems there is some invalid value for the column line 0 that is not a valid foreign key so MySQL cannot set a foreign key constraint for it.

You can follow these steps:

1. Drop the column which you have tried to set FK constraint for.

2. Add it again and set its default value as NULL.

3. Try to set a foreign key constraint for it again.