Administrative privileges enable users to manage operation of the MySQL server. These privileges are global because they are not specific to a particular database.

Database privileges apply to a database and to all objects within it. These privileges can be granted for specific databases, or globally so that they apply to all databases.

Privileges for database objects such as tables, indexes, views, and stored routines can be granted for specific objects within a database, for all objects of a given type within a database (for example, all tables in a database), or globally for all objects of a given type in all databases).

The ALL or ALL PRIVILEGES privilege specifier is shorthand. It stands for “all privileges available at a given privilege level” (except GRANT OPTION). For example, granting ALL at the global or table level grants all global privileges or all table-level privileges.

The ALTER privilege enables use of ALTER TABLE to change the structure of or rename tables. (ALTER TABLE also requires the INSERT and CREATE privileges.)

The CREATE privilege enables creation of new databases and tables.

The CREATE TEMPORARY TABLES privilege enables the use of the keyword TEMPORARY in CREATE TABLE statements. This privilege was added in MySQL 4.0.2.

The DELETE privilege enables rows to be deleted from tables in a database.

The DROP privilege enables you to drop (remove) existing databases and tables. If you grant the DROP privilege for the mysql database to a user, that user can drop the database in which the MySQL access privileges are stored!

The EXECUTE privilege was added in MySQL 4.0.2, but is not used until MySQL 5.0.

The FILE privilege gives you permission to read and write files on the server host using the LOAD DATA INFILE and SELECT ... INTO OUTFILE statements and the LOAD_FILE() function. A user who has the FILE privilege can read any file on the server host that is either world-readable or readable by the MySQL server. (This implies the user can read any file in any database directory, because the server can access any of those files.) The FILE privilege also enables the user to create new files in any directory where the MySQL server has write access. As a security measure, the server will not overwrite existing files.

The GRANT OPTION privilege enables you to give to other users or remove from other users those privileges that you yourself possess.

The INDEX privilege enables you to create or drop (remove) indexes. INDEX applies to existing tables. If you have the CREATE privilege for a table, you can include index definitions in the CREATE TABLE statement.

The INSERT privilege enables rows to be inserted into tables in a database. INSERT is also required for the ANALYZE TABLE, OPTIMIZE TABLE, and REPAIR TABLE table-maintenance statements.

The LOCK TABLES privilege enables the use of explicit LOCK TABLES statements to lock tables for which you have the SELECT privilege. This includes the use of write locks, which prevents other sessions from reading the locked table. This privilege was added in MySQL 4.0.2.

The PROCESS privilege pertains to display of information about the threads executing within the server (that is, information about the statements being executed by sessions). The privilege enables use of SHOW PROCESSLIST or mysqladmin processlist to see threads belonging to other accounts; you can always see your own threads. Prior to MySQL 4.0.2, PROCESS also enable the use of KILL to kill threads belonging to other accounts; you can always kill your own threads.

The REFERENCES privilege currently is unused.

The RELOAD privilege enables use of the FLUSH statement. It also enables mysqladmin commands that are equivalent to FLUSH operations: flush-hosts, flush-logs, flush-privileges, flush-status, flush-tables, flush-threads, refresh, and reload.

The reload command tells the server to reload the grant tables into memory. flush-privileges is a synonym for reload. The refresh command closes and reopens the log files and flushes all tables. The other flush-xxx commands perform functions similar to refresh, but are more specific and may be preferable in some instances. For example, if you want to flush just the log files, flush-logs is a better choice than refresh.

The REPLICATION CLIENT privilege enables the use of SHOW MASTER STATUS and SHOW SLAVE STATUS. This privilege was added in MySQL 4.0.2.

The REPLICATION SLAVE privilege should be granted to accounts that are used by slave servers to connect to the current server as their master. Without this privilege, the slave cannot request updates that have been made to databases on the master server. This privilege was added in MySQL 4.0.2.

The SELECT privilege enables you to select rows from tables in a database. SELECT statements require the SELECT privilege only if they actually retrieve rows from a table. Some SELECT statements do not access tables and can be executed without permission for any database. For example, you can use SELECT as a simple calculator to evaluate expressions that make no reference to tables:

SELECT 1+1;
SELECT PI()*2;

The SELECT privilege is also needed for other statements that read column values. For example, SELECT is needed for columns referenced on the right hand side of col_name=expr assignment in UPDATE statements or for columns named in the WHERE clause of DELETE or UPDATE statements.

The SHOW DATABASES privilege enables the account to see database names by issuing the SHOW DATABASE statement. Accounts that do not have this privilege see only databases for which they have some privileges, and cannot use the statement at all if the server was started with the --skip-show-database option. Note that any global privilege is a privilege for the database. SHOW DATABASES was added in MySQL 4.0.2.

MySQL Enterprise.  The SHOW DATABASES privilege should be granted only to users who need to see all the databases on a MySQL server. Subscribers to the MySQL Enterprise Monitor are alerted when servers are started without the --skip-show-database option. For more information, see http://www.mysql.com/products/enterprise/advisors.html.

The SHUTDOWN privilege enables use of the mysqladmin shutdown command. There is no corresponding SQL statement.

The SUPER privilege enables an account to use CHANGE MASTER TO, KILL or mysqladmin kill to kill threads belonging to other accounts (you can always kill your own threads), PURGE BINARY LOGS, configuration changes via SET GLOBAL to modify global system variables, the mysqladmin debug command, enabling or disabling logging, performing updates even if the read_only system variable is enabled, starting and stopping replication on slave servers, and allows you to connect (once) even if the connection limit controlled by the max_connections system variable is reached. This privilege was added in MySQL 4.0.2. Prior to MySQL 4.0.2, the PROCESS privilege controls the ability to terminate threads for other accounts.

The UPDATE privilege enables rows to be updated in tables in a database.

The USAGE privilege specifier stands for “no privileges.” It is used at the global level with GRANT to modify account attributes such as resource limits or SSL characteristics without affecting existing account privileges.

The FILE privilege can be abused to read into a database table any files that the MySQL server can read on the server host. This includes all world-readable files and files in the server's data directory. The table can then be accessed using SELECT to transfer its contents to the client host.

The GRANT OPTION privilege enables users to give their privileges to other users. Two users that have different privileges and with the GRANT OPTION privilege are able to combine privileges.

The ALTER privilege may be used to subvert the privilege system by renaming tables.

The SHUTDOWN privilege can be abused to deny service to other users entirely by terminating the server.

The PROCESS privilege can be used to view the plain text of currently executing statements, including statements that set or change passwords.

The SUPER privilege can be used to terminate other sessions or change how the server operates.

Privileges granted for the mysql database itself can be used to change passwords and other access privilege information. Passwords are stored encrypted, so a malicious user cannot simply read them to know the plain text password. However, a user with write access to the user table Password column can change an account's password, and then connect to the MySQL server using that account.

MySQL Enterprise.  Accounts with unnecessary global privileges constitute a security risk. Subscribers to the MySQL Enterprise Monitor are automatically alerted to the existence of such accounts. For detailed information, see http://www.mysql.com/products/enterprise/advisors.html.