MySQL Error 1215: Cannot add foreign key constraint

Question

I am trying to forward engineer my new schema onto my db server, but I can\'t figure out why I am getting this error. I\'ve tried to search for the answer here, but everyth

Answer 1

I know i am VERY late to the party but i want to put it out here so that it is listed.

As well as all of the above advice for making sure that fields are identically defined, and table types also have the same collation, make sure that you don't make the rookie mistake of trying to link fields where data in the CHILD field is not already in the PARENT field. If you have data that is in the CHILD field that you have not already entered in to the PARENT field then that will cause this error. It's a shame that the error message is not a bit more helpful.

If you are unsure, then backup the table that has the Foreign Key, delete all the data and then try to create the Foreign Key. If successful then you what to do!

Good luck.