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 KEY Constraint Differences.
MySQL Workbench enables you to add a foreign key from within the table editor or from within an EER diagram by using the relationship tools on the vertical toolbar. This section describes how to add a foreign key using the foreign key tools. To add a foreign key using the table editor, see Section 18.104.22.168, “Foreign Keys Tab”.
The graphical tools for adding foreign keys are most effective when you are building tables from the ground up. If you have imported a database using an SQL script and need not add columns to your tables, you may find it more effective to define foreign keys using the table editor.