MAN page from RedHat EL 5 MySQL-client-community-5.1.72-1.rhel5.x86_64.rpm


Section: MySQL Database System (1)
Updated: 09/09/2013


mysqlcheck - a table maintenance program 


mysqlcheck [options] [db_name [tbl_name ...]]


Themysqlcheckclient performs table maintenance: It checks, repairs, optimizes, or analyzes tables.

Each table is locked and therefore unavailable to other sessions while it is being processed, although for check operations, the table is locked with aREADlock only (seeSection 13.3.5, lqLOCK TABLES and UNLOCK TABLES Syntaxrq, for more information aboutREADandWRITElocks). Table maintenance operations can be time-consuming, particularly for large tables. If you use the--databasesor--all-databasesoption to process all tables in one or more databases, an invocation ofmysqlcheckmight take a long time. (This is also true formysql_upgradebecause that program invokesmysqlcheckto check all tables and repair them if necessary.)

mysqlcheckis similar in function tomyisamchk, but works differently. The main operational difference is thatmysqlcheckmust be used when themysqldserver is running, whereasmyisamchkshould be used when it is not. The benefit of usingmysqlcheckis that you do not have to stop the server to perform table maintenance.

mysqlcheckuses the SQL statementsCHECK TABLE,REPAIR TABLE,ANALYZE TABLE, andOPTIMIZE TABLEin a convenient way for the user. It determines which statements to use for the operation you want to perform, and then sends the statements to the server to be executed. For details about which storage engines each statement works with, see the descriptions for those statements inSection 13.7.2, lqTable Maintenance Statementsrq.

TheMyISAMstorage engine supports all four maintenance operations, somysqlcheckcan be used to perform any of them onMyISAMtables. Other storage engines do not necessarily support all operations. In such cases, an error message is displayed. For example, iftest.tis aMEMORYtable, an attempt to check it produces this result:

shell> mysqlcheck test ttest.tnote     : The storage engine for the table doesn't support check

Ifmysqlcheckis unable to repair a table, seeSection 2.13.4, lqRebuilding or Repairing Tables or Indexesrqfor manual table repair strategies. This will be the case, for example, forInnoDBtables, which can be checked withCHECK TABLE, but not repaired withREPAIR TABLE.

The use ofmysqlcheckwith partitioned tables is not supported before MySQL 5.1.27.


It is best to make a backup of a table before performing a table repair operation; under some circumstances the operation might cause data loss. Possible causes include but are not limited to file system errors.

There are three general ways to invokemysqlcheck:

shell> mysqlcheck [options] db_name [tbl_name ...]shell> mysqlcheck [options] --databases db_name> mysqlcheck [options] --all-databases

If you do not name any tables followingdb_nameor if you use the--databasesor--all-databasesoption, entire databases are checked.

mysqlcheckhas a special feature compared to other client programs. The default behavior of checking tables (--check) can be changed by renaming the binary. If you want to have a tool that repairs tables by default, you should just make a copy ofmysqlchecknamedmysqlrepair, or make a symbolic link tomysqlchecknamedmysqlrepair. If you invokemysqlrepair, it repairs tables.

The names shown in the following table can be used to changemysqlcheckdefault behavior.
mysqlrepairThe default option is --repair
mysqlanalyzeThe default option is --analyze
mysqloptimizeThe default option is --optimize

mysqlchecksupports the following options, which can be specified on the command line or in the[mysqlcheck]and[client]groups of an option file.mysqlcheckalso supports the options for processing option files described atSection, lqCommand-Line Options that Affect Option-File Handlingrq.


Display a help message and exit.


Check all tables in all databases. This is the same as using the--databasesoption and naming all the databases on the command line.


Instead of issuing a statement for each table, execute a single statement for each database that names all the tables from that database to be processed.


Analyze the tables.


If a checked table is corrupted, automatically fix it. Any necessary repairs are done after all tables have been checked.


On a computer having multiple network interfaces, this option can be used to select which interface is employed when connecting to the MySQL server.

This option is supported only in the version ofmysqlcheckthat is supplied with MySQL Cluster, beginning with MySQL Cluster NDB 6.3.4. It is not available in standard MySQL 5.1 releases.


The directory where character sets are installed. SeeSection 10.5, lqCharacter Set Configurationrq.


Check the tables for errors. This is the default operation.


Check only tables that have changed since the last check or that have not been closed properly.


InvokeCHECK TABLEwith theFOR UPGRADEoption to check tables for incompatibilities with the current version of the server. This option automatically enables the--fix-db-namesand--fix-table-namesoptions.--check-upgradewas added in MySQL 5.1.7.


Compress all information sent between the client and the server if both support compression.


Process all tables in the named databases. Normally,mysqlchecktreats the first name argument on the command line as a database name and following names as table names. With this option, it treats all name arguments as database names.

*--debug[=debug_options],-# [debug_options]

Write a debugging log. A typicaldebug_optionsstring is'd:t:o,file_name'. The default is'd:t:o'.


Print some debugging information when the program exits. This option was added in MySQL 5.1.21.


Print debugging information and memory and CPU usage statistics when the program exits. This option was added in MySQL 5.1.14.


Usecharset_nameas the default character set. SeeSection 10.5, lqCharacter Set Configurationrq.


If you are using this option to check tables, it ensures that they are 100% consistent but takes a long time.

If you are using this option to repair tables, it runs an extended repair that may not only take a long time to execute, but may produce a lot of garbage rows also!


Check only tables that have not been closed properly.


Convert database names to 5.1 format. Only database names that contain special characters are affected. This option was added in MySQL 5.1.7.


Convert table names to 5.1 format. Only table names that contain special characters are affected. This option was added in MySQL 5.1.7. As of MySQL 5.1.23, this option also applies to views.


Continue even if an SQL error occurs.

*--host=host_name,-h host_name

Connect to the MySQL server on the given host.


Do a check that is faster than an--extendedoperation. This finds only 99.99% of all errors, which should be good enough in most cases.


Optimize the tables.


The password to use when connecting to the server. If you use the short option form (-p), youcannothave a space between the option and the password. If you omit thepasswordvalue following the--passwordor-poption on the command line,mysqlcheckprompts for one.

Specifying a password on the command line should be considered insecure. SeeSection, lqEnd-User Guidelines for Password Securityrq. You can use an option file to avoid giving the password on the command line.


On Windows, connect to the server using a named pipe. This option applies only if the server supports named-pipe connections.

*--port=port_num,-P port_num

The TCP/IP port number to use for the connection.


The connection protocol to use for connecting to the server. It is useful when the other connection parameters normally would cause a protocol to be used other than the one you want. For details on the permissible values, seeSection 4.2.2, lqConnecting to the MySQL Serverrq.


If you are using this option to check tables, it prevents the check from scanning the rows to check for incorrect links. This is the fastest check method.

If you are using this option to repair tables, it tries to repair only the index tree. This is the fastest repair method.


Perform a repair that can fix almost anything except unique keys that are not unique.


Silent mode. Print only error messages.

*--socket=path,-S path

For connections tolocalhost, the Unix socket file to use, or, on Windows, the name of the named pipe to use.


Options that begin with--sslspecify whether to connect to the server using SSL and indicate where to find SSL keys and certificates. SeeSection, lqSSL Command Optionsrq.


Override the--databasesor-Boption. All name arguments following the option are regarded as table names.


For repair operations onMyISAMtables, get the table structure from the.frmfile so that the table can be repaired even if the.MYIheader is corrupted.

*--user=user_name,-u user_name

The MySQL user name to use when connecting to the server.


Verbose mode. Print information about the various stages of program operation.


Display version information and exit.


This option is enabled by default, so thatANALYZE TABLE,OPTIMIZE TABLE, andREPAIR TABLEstatements generated bymysqlcheckare written to the binary log. Use--skip-write-binlogto causeNO_WRITE_TO_BINLOGto be added to the statements so that they are not logged. Use the--skip-write-binlogwhen these statements should not be sent to replication slaves or run when using the binary logs for recovery from backup. This option was added in MySQL 5.1.18.



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