Foreign keys must be Index in mySQL?

Question

I\'ve just created my first mySQL table on my own (other than using Joomla, Wordpress, etc.) and I am MS SQL developer for years but normally I can easily create a foreign key i

Answer 1

From the documentation:

InnoDB requires indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan. In the referencing table, there must be an index where the foreign key columns are listed as the first columns in the same order.