Foreign key constraints are supported for the InnoDB storage engine only. For other storage engines the foreign key syntax is correctly parsed but not implemented. For more information see Foreign Keys.

Using MySQL Workbench you may add a foreign key from within the table editor or by using the relationship tools on the vertical toolbar of an EER Diagram. This section deals with adding a foreign key using the foreign key tools. To add a foreign key using the table editor see Section 7.5.1.3.5, “The Foreign Keys Tab”.

Using the graphical tools to add foreign keys is most effective when you are building tables from the ground up. If you have imported a database using an SQL script and do not need to add fields to your tables you may find it more effective to define foreign keys using the table editor.