The GRANT and REVOKE statements allow system administrators to
create MySQL user accounts and to grant rights to and revoke them from
accounts.  GRANT and REVOKE are implemented in MySQL 3.22.11
or later. For earlier MySQL versions, these statements do nothing.

MySQL account information is stored in the tables of the mysql
database. This database and the access control system are discussed
extensively in [MySQL Database Administration], which you should consult
for additional details.

Privileges can be granted at four levels:

   Global level
Global privileges apply to all databases on a given server. These privileges
are stored in the mysql.user table.
GRANT ALL ON *.* and
REVOKE ALL ON *.* grant and revoke only global privileges.

   Database level
Database privileges apply to all tables in a given database. These privileges
are stored in the mysql.db and mysql.host tables.
GRANT ALL ON db_name.* and
REVOKE ALL ON db_name.* grant and revoke only database privileges.

   Table level
Table privileges apply to all columns in a given table. These privileges are
stored in the mysql.tables_priv table.
GRANT ALL ON db_name.tbl_name and
REVOKE ALL ON db_name.tbl_name grant and revoke only table privileges.

   Column level
Column privileges apply to single columns in a given table. These privileges are
stored in the mysql.columns_priv table.
When using REVOKE, you must specify the same columns that were granted.
  
