MySQL account information is stored in the tables of the
mysql database. This database and the access
control system are discussed extensively in
Chapter 5, MySQL Server Administration, which you should consult
for additional details.
Some releases of MySQL introduce changes to the structure of the grant tables to add new privileges or features. To make sure that you can take advantage of any new capabilities, update your grant tables to have the current structure whenever you update to a new version of MySQL. See Section 4.4.6, “mysql_upgrade — Check and Upgrade MySQL Tables”.