Mysql cannot add or update child row, Foreign key related failure

Question

Error: cannot add or update a child row: foreign key constraint fails

Following is the code that is creating the error:

ALTER TABLE 'catalog_eav_attribute' 
  ADD CONSTRAINT 'FK_CATALOG_EAV_ATTRIBUTE_ID' 
  FOREIGN KEY ('attribute_id') REFERENCES 'eav_attribute' ('attribute_id)' 
  ON DELETE CASCADE ON UPDATE CASCADE;

I uploaded the Structure of SQL and its has no issue , but when i insert the data i am getting the above related error. I read somewhere and i predict its because of lousy data.What are the other possibilities for the error ? Any suggestions or solution will be great.

Answer 1

"For storage engines other than InnoDB, MySQL Server parses the FOREIGN KEY syntax in CREATE TABLE statements, but does not use or store it."

From: http://dev.mysql.com/doc/refman/5.5/en/ansi-diff-foreign-keys.html

I'm not sure, but if your table is MyISAM and not InnoDB, your syntax might not work.

Answer 2

The error message means whatever number you're trying to put into the attribute_id column doesn't yet exist in the eav_attribute.attribute_id column.

Can you insert a value that does already exist in eav_attribute.attribute_id? (You probably can.)

Can you provoke the same error by trying to insert a value that doesn't exist in eav_attribute.attribute_id?

Reconcile the differences, and you're done. You need to determine which attribute ids don't exist in eav_attribute.attribute_id, and fix that.