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4.5.4 mysqldump — A Database Backup Program

The mysqldump client is a backup program originally written by Igor Romanenko. It can be used to dump a database or a collection of databases for backup or transfer to another SQL server (not necessarily a MySQL server). The dump typically contains SQL statements to create the table, populate it, or both. However, mysqldump can also be used to generate files in CSV, other delimited text, or XML format.

mysqldump requires at least the SELECT privilege for dumped tables, SHOW VIEW for dumped views, SUPER for dumped triggers, and LOCK TABLES if the --single-transaction option is not used. Certain options might require other privileges as noted in the option descriptions.

To reload a dump file, you must have the privileges required to execute the statements that it contains, such as the appropriate CREATE privileges for objects created by those statements.

If you are doing a backup on the server and your tables all are MyISAM tables, consider using the mysqlhotcopy instead because it can accomplish faster backups and faster restores. See Section 4.6.9, “mysqlhotcopy — A Database Backup Program”.

There are three general ways to invoke mysqldump:

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

If you do not name any tables following db_name or if you use the --databases or --all-databases option, entire databases are dumped.

mysqldump does not dump the INFORMATION_SCHEMA database. If you name that database explicitly on the command line, mysqldump silently ignores it.

To see a list of the options your version of mysqldump supports, execute mysqldump --help.

Some mysqldump options are shorthand for groups of other options:

To reverse the effect of a group option, uses its --skip-xxx form (--skip-opt or --skip-compact). It is also possible to select only part of the effect of a group option by following it with options that enable or disable specific features. Here are some examples:

When you selectively enable or disable the effect of a group option, order is important because options are processed first to last. For example, --disable-keys --lock-tables --skip-opt would not have the intended effect; it is the same as --skip-opt by itself.

mysqldump can retrieve and dump table contents row by row, or it can retrieve the entire content from a table and buffer it in memory before dumping it. Buffering in memory can be a problem if you are dumping large tables. To dump tables row by row, use the --quick option (or --opt, which enables --quick). The --opt option (and hence --quick) is enabled by default, so to enable memory buffering, use --skip-quick.

If you are using a recent version of mysqldump to generate a dump to be reloaded into a very old MySQL server, you should not use the --opt or --extended-insert option. Use --skip-opt instead.

Before MySQL 4.1.2, out-of-range numeric values such as -inf and inf, as well as NaN (not-a-number) values are dumped by mysqldump as NULL. You can see this using the following sample table:

mysql> INSERT INTO t VALUES(1e+111111111111111111111);
mysql> INSERT INTO t VALUES(-1e111111111111111111111);
mysql> SELECT f FROM t;
| f    |
|  inf |
| -inf |

For this table, mysqldump produces the following data output:

-- Dumping data for table `t`


The significance of this behavior is that if you dump and restore the table, the new table has contents that differ from the original contents. This problem is fixed as of MySQL 4.1.2; you cannot insert inf in the table, so this mysqldump behavior is only relevant when you deal with old servers.

For additional information about mysqldump, see Section 7.4, “Using mysqldump for Backups”.

mysqldump supports the following options, which can be specified on the command line or in the [mysqldump] and [client] groups of an option file. For information about option files used by MySQL programs, see Section 4.2.6, “Using Option Files”.

Table 4.6 mysqldump Options

--add-drop-databaseAdd DROP DATABASE statement before each CREATE DATABASE statement 
--add-drop-tableAdd DROP TABLE statement before each CREATE TABLE statement 
--add-locksSurround each table dump with LOCK TABLES and UNLOCK TABLES statements 
--all-databasesDump all tables in all databases 
--allow-keywordsAllow creation of column names that are keywords 
--character-sets-dirDirectory where character sets are installed 
--commentsAdd comments to dump file 
--compactProduce more compact output 
--compatibleProduce output that is more compatible with other database systems or with older MySQL servers 
--complete-insertUse complete INSERT statements that include column names 
--compressCompress all information sent between client and server 
--create-optionsInclude all MySQL-specific table options in CREATE TABLE statements 
--databasesInterpret all name arguments as database names 
--debugWrite debugging log 
--debug-infoPrint debugging information, memory, and CPU statistics when program exits5.0.32
--default-character-setSpecify default character set 
--defaults-extra-fileRead named option file in addition to usual option files 
--defaults-fileRead only named option file 
--defaults-group-suffixOption group suffix value5.0.10
--delayed-insertWrite INSERT DELAYED statements rather than INSERT statements 
--delete-master-logsOn a master replication server, delete the binary logs after performing the dump operation 
--disable-keysFor each table, surround INSERT statements with statements to disable and enable keys 
--dump-dateInclude dump date as "Dump completed on" comment if --comments is given5.0.52
--extended-insertUse multiple-row INSERT syntax 
--fields-enclosed-byThis option is used with the --tab option and has the same meaning as the corresponding clause for LOAD DATA INFILE 
--fields-escaped-byThis option is used with the --tab option and has the same meaning as the corresponding clause for LOAD DATA INFILE 
--fields-optionally-enclosed-byThis option is used with the --tab option and has the same meaning as the corresponding clause for LOAD DATA INFILE 
--fields-terminated-byThis option is used with the --tab option and has the same meaning as the corresponding clause for LOAD DATA INFILE 
--first-slaveDeprecated; use --lock-all-tables instead 
--flush-logsFlush MySQL server log files before starting dump 
--flush-privilegesEmit a FLUSH PRIVILEGES statement after dumping mysql database 
--forceContinue even if an SQL error occurs during a table dump 
--helpDisplay help message and exit 
--hex-blobDump binary columns using hexadecimal notation 
--hostHost to connect to (IP address or hostname) 
--ignore-tableDo not dump given table 
--insert-ignoreWrite INSERT IGNORE rather than INSERT statements 
--lines-terminated-byThis option is used with the --tab option and has the same meaning as the corresponding clause for LOAD DATA INFILE 
--lock-all-tablesLock all tables across all databases 
--lock-tablesLock all tables before dumping them 
--log-errorAppend warnings and errors to named file5.0.42
--master-dataWrite the binary log file name and position to the output 
--max_allowed_packetMaximum packet length to send to or receive from server 
--net_buffer_lengthBuffer size for TCP/IP and socket communication 
--no-autocommitEnclose the INSERT statements for each dumped table within SET autocommit = 0 and COMMIT statements 
--no-create-dbDo not write CREATE DATABASE statements 
--no-create-infoDo not write CREATE TABLE statements that re-create each dumped table 
--no-dataDo not dump table contents 
--no-defaultsRead no option files 
--no-set-namesSame as --skip-set-charset 
--optShorthand for --add-drop-table --add-locks --create-options --disable-keys --extended-insert --lock-tables --quick --set-charset. 
--order-by-primaryDump each table's rows sorted by its primary key, or by its first unique index 
--passwordPassword to use when connecting to server 
--pipeOn Windows, connect to server using named pipe 
--portTCP/IP port number to use for connection 
--print-defaultsPrint default options 
--protocolConnection protocol to use 
--quickRetrieve rows for a table from the server a row at a time 
--quote-namesQuote identifiers within backtick characters 
--result-fileDirect output to a given file 
--routinesDump stored routines (procedures and functions) from dumped databases5.0.13
--set-charsetAdd SET NAMES default_character_set to output 
--shared-memory-base-nameThe name of shared memory to use for shared-memory connections 
--single-transactionIssue a BEGIN SQL statement before dumping data from server 
--skip-add-drop-tableDo not add a DROP TABLE statement before each CREATE TABLE statement 
--skip-add-locksDo not add locks 
--skip-commentsDo not add comments to dump file 
--skip-compactDo not produce more compact output 
--skip-disable-keysDo not disable keys 
--skip-extended-insertTurn off extended-insert 
--skip-optTurn off options set by --opt 
--skip-quickDo not retrieve rows for a table from the server a row at a time 
--skip-quote-namesDo not quote identifiers 
--skip-set-charsetDo not write SET NAMES statement 
--skip-triggersDo not dump triggers5.0.11
--skip-tz-utcTurn off tz-utc5.0.15
--socketFor connections to localhost, the Unix socket file to use 
--sslEnable secure connection 
--ssl-caPath of file that contains list of trusted SSL CAs 
--ssl-capathPath of directory that contains trusted SSL CA certificates in PEM format 
--ssl-certPath of file that contains X509 certificate in PEM format 
--ssl-cipherList of permitted ciphers to use for connection encryption 
--ssl-keyPath of file that contains X509 key in PEM format 
--ssl-verify-server-certVerify server certificate Common Name value against host name used when connecting to server5.0.23
--tabProduce tab-separated data files 
--tablesOverride --databases or -B option 
--triggersDump triggers for each dumped table 
--tz-utcAdd SET TIME_ZONE='+00:00' to dump file5.0.15
--userMySQL user name to use when connecting to server 
--verboseVerbose mode 
--versionDisplay version information and exit 
--whereDump only rows selected by given WHERE condition 
--xmlProduce XML output 

You can also set the following variables by using --var_name=value syntax:

It is also possible to set variables by using --var_name=value. The --set-variable format is deprecated.

A common use of mysqldump is for making a backup of an entire database:

shell> mysqldump db_name > backup-file.sql

You can load the dump file back into the server like this:

shell> mysql db_name < backup-file.sql

Or like this:

shell> mysql -e "source /path-to-backup/backup-file.sql" db_name

mysqldump is also very useful for populating databases by copying data from one MySQL server to another:

shell> mysqldump --opt db_name | mysql --host=remote_host -C db_name

It is possible to dump several databases with one command:

shell> mysqldump --databases db_name1 [db_name2 ...] > my_databases.sql

To dump all databases, use the --all-databases option:

shell> mysqldump --all-databases > all_databases.sql

For InnoDB tables, mysqldump provides a way of making an online backup:

shell> mysqldump --all-databases --master-data --single-transaction > all_databases.sql

This backup acquires a global read lock on all tables (using FLUSH TABLES WITH READ LOCK) at the beginning of the dump. As soon as this lock has been acquired, the binary log coordinates are read and the lock is released. If long updating statements are running when the FLUSH statement is issued, the MySQL server may get stalled until those statements finish. After that, the dump becomes lock free and does not disturb reads and writes on the tables. If the update statements that the MySQL server receives are short (in terms of execution time), the initial lock period should not be noticeable, even with many updates.

For point-in-time recovery (also known as roll-forward, when you need to restore an old backup and replay the changes that happened since that backup), it is often useful to rotate the binary log (see Section 5.4.3, “The Binary Log”) or at least know the binary log coordinates to which the dump corresponds:

shell> mysqldump --all-databases --master-data=2 > all_databases.sql


shell> mysqldump --all-databases --flush-logs --master-data=2
              > all_databases.sql

The --master-data and --single-transaction options can be used simultaneously, which provides a convenient way to make an online backup suitable for use prior to point-in-time recovery if tables are stored using the InnoDB storage engine.

For more information on making backups, see Section 7.2, “Database Backup Methods”, and Section 7.3, “Example Backup and Recovery Strategy”.

If you encounter problems backing up views, please read the section that covers restrictions on views which describes a workaround for backing up views when this fails due to insufficient privileges. See Section C.4, “Restrictions on Views”.