The Relational System - Mastering phpMyAdmin 3.1 for Effective MySQL Management - page 187

This operation exists because for tables under the storage engines that do not support
foreign key natively, neither MySQL nor phpMyAdmin enforce referential integrity.
It is perfectly possible, for example, to import data in the book 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 this column
in the metadata for the relation. This guarantees an internal relation continues to
function, even after a column's name is changed. The same thing happens when a
column or table is dropped.
Metadata should be maintained manually in case a change in the
structure is done from outside phpMyAdmin.
Column-commenting
Prior to MySQL 4.1, the MySQL structure itself did not support the addition of
comments to a column. Nevertheless, thanks to phpMyAdmin's metadata—we could
comment on columns. However, since MySQL 4.1, native column commenting has
been supported. The good news is that for any MySQL version, column commenting
in phpMyAdmin is always accessed via the Structure page by editing the structure of
each field. In the following example, we need to comment three columns. Hence, we
choose them and click the pencil icon near the With selected choice.