Can you do a foreign key within a single table, though? I've only ever seen foreign key constraints tying a field in one table to a field in another table.

Indexes in MySQL are used to speed up access in the database and help enforce database constraints (such as UNIQUE and FOREIGN KEY). Database indexes are much like book indexes.

Merging Tables with MySQL Merging tables, called "joining" in MySQL terms, is done by using the MySQL command interface in phpMyAdmin to create a new table.