The Relational System - Mastering phpMyAdmin 2.11 for Effective MySQL Management - page 183

Moving the mouse pointer over any author_id value reveals the author's name
(as defined by the display field of the author table):
Clicking on the author_id brings us to the relevant table, author , for this
specific author:
The Drop-Down List of Foreign Keys
Going back to the book table, in Insert mode (or in Edit mode), we now see a
drop-down list of the possible keys for each field that has a relation defined. The list
contains the keys and the description (display field) in both orders: key to display
field, and display field to key. This enables us to use the keyboard and type the first
letter of either the key or the display field:
Only the key (in this case 1 ) will be stored in the book table. The display
field is only there to assist us.
By default, this drop-down list will appear if there are a maximum of 100 rows in the
foreign table. This is controlled by the following parameter:
$cfg['ForeignKeyMaxLimit'] = 100;
For foreign tables bigger than that, a distinct window appears: the browseable
foreign-table window.