The Relational System - Mastering phpMyAdmin 2.8 for Effective MySQL Management - page 172

This operation exists, because for non-InnoDB tables, MySQL does not enforce
referential integrity, and neither does phpMyAdmin. It is perfectly possible, for
example, to import data in the books table with invalid values for author_id .
Automatic Updates of Metadata
phpMyAdmin keeps the metadata for internal relations synchronized with every
change that is made to the tables via phpMyAdmin. For example, renaming a column
that is part of a relation would make phpMyAdmin rename it also in the metadata
for the relation. The same thing happens when a column or a table is dropped.
Metadata should be manually maintained in case a change
in the structure is done from outside phpMyAdmin.
Column-Commenting
Before MySQL 4.1, the MySQL structure itself does not support adding comments to a
column. Thanks to phpMyAdmin's metadata, we can nevertheless comment columns.
Since MySQL 4.1, native column commenting is supported. The good news is that for
any MySQL version, column commenting via phpMyAdmin is always accessed via
the Structure page by editing each field's structure. In the following example, we need
to comment three columns, so we choose them and click the pencil icon: