MySQL in a Nutshell [26]
As of version 5.1 of MySQL, FLUSH cannot be used in stored functions and triggers, but can be used in stored procedures. As an alternative to the FLUSH statement, you can use the mysqladmin command (see Chapter 16).
Table 4-1. Options for FLUSH statement
Option
Explanation
DES_KEY_FILE
Reloads the DES encryption file, which is given with the --des-key-file option at startup or in the options file.
HOSTS
Clears the hosts cache, which is used to minimize host/IP address lookups. The hosts cache may need to be flushed if a host has been blocked from accessing the server.
LOGS
Used to close all of the log files and reopen them. If the server has binary logging enabled, it will change the binary log file to the next in numeric sequence. If the error log was enabled, it will rename the error log to the same name, but with the ending -old, and start a new error log. This option is not logged.
MASTER
This option is not logged and has been deprecated. Use the RESET MASTER statement instead.
PRIVILEGES
Reloads the grant tables for user privileges. This is necessary if the user table in the mysql database has been modified manually, without the GRANT statement.
QUERY CACHE
Instructs the server to defragment the query cache to improve performance. It doesn’t remove queries from cache, though. Use the RESET QUERY CACHE statement to remove the queries.
SLAVE
This option is not logged and has been deprecated. Use the RESET SLAVE statement instead.
STATUS
Resets the session values and counters for key caches to 0. The current thread’s session status variables are set to those of the global variables. The max_used_conections variable is set to the number of sessions open at the time.
TABLE[ table, ...]
Followed by one or more table names, this option forces the given tables to be closed. This will terminate any active queries on the given tables. Specified without any tables, the option has the same effect as TABLES.
TABLES
Causes all tables to be closed, all queries to be terminated, and the query cache to be flushed. This is the same as TABLE with no table name.
TABLES WITH READ LOCK
Closes all tables and locks them with a global read lock. This will allow users to view the data, but not to update it or insert records. The lock will remain in place until the UNLOCK TABLES statement is executed. This option is not logged.
USER_RESOURCES
Resets all user resource values that are calculated on an hourly basis. These are the values for the columns max_questions, max_updates, and max_connections in the user table of the mysql database. Use this FLUSH option when users have been blocked because they exceed hourly limits. If these columns are missing, see Chapter 16 for the explanation of mysql_fix_privilege_tables.
Name
GRANT
Synopsis
GRANT privilege[,...] [(column[,...])][, ...]
ON [TABLE|FUNCTION|PROCEDURE] {[{database|*}.{table|*}] | *}
TO 'user'@'host' [IDENTIFIED BY [PASSWORD] 'password'][, ...]
[REQUIRE NONE |
[{SSL|X509}] [CIPHER 'cipher' [AND]]
[ISSUER 'issue' [AND]]
[SUBJECT 'subject']]
[WITH [GRANT OPTION |
MAX_QUERIES_PER_HOUR count |
MAX_UPDATES_PER_HOUR count |
MAX_CONNECTIONS_PER_HOUR count |
MAX_USER_CONNECTIONS count] ...]
This statement may be used to create new MySQL users, but its primary use is for granting user privileges. Privileges can be global (apply to all databases on the server), database-specific, table-specific, or column-specific. Users can now also be limited by functions and procedures. Additionally, users can be limited by number of connections or by a maximum of resources per hour.
The privileges to grant to a user are listed immediately after the GRANT keyword in a comma-separated list. To restrict a user to specific columns in a table,