Securing the Database - Database Design Manual: Using MySQL for Windows - page 139

Figure 12.7 DESCRIBE tables_priv.

Figure 12.8 Mary's entry in the tables_priv table.

Figure 12.9 shows what happens if we view the tables_priv table after running the
GRANT query above. If you compare it with Figure 12.8 you will see that instead of adding
another row for the INSERT privilege it has appended the first entry. The tables_priv col-
umn now reads Select and Insert.

The Grant Tables

The user and tables_priv tables are known as the grant tables. These tables control every-
one's access to your MySQL server. There are five grant tables in all, as shown in Table 12.1.
All of these tables are stored within the mysql database, so you can refer to them directly
when using GRANT or REVOKE by adding mysql. to the front of the table name, i.e.
mysql.db , mysql.tables_priv , mysql.columns_priv ,etc.
Generally, you do not need to know what is going on within all of these tables, as long as
you understand how the GRANT and REVOKE queries work. However, it is useful to real-
ize that MySQL uses its own tables to store the privileges in, and you can access these using
the normal query mechanisms.