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MYSQLDUMP(1) MySQL Database System MYSQLDUMP(1)
NAME
mysqldump - a database backup program
SYNOPSIS
mysqldump [options] [db_name [tbl_name ...]]
DESCRIPTION
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 for transferring the data to another SQL server
(not necessarily a MySQL server). The dump contains SQL statements to
create the table or populate it, or both.
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 mysqlhotcopy(1).
There are three general ways to invoke mysqldump:
shell> mysqldump [options] db_name [tables]
shell> mysqldump [options] --databases db_name1 [db_name2 db_name3...]
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.
To get a list of the options your version of mysqldump supports,
execute mysqldump --help.
If you run mysqldump without the --quick or --opt option, mysqldump
loads the whole result set into memory before dumping the result. This
can be a problem if you are dumping a big database. As of MySQL 4.1,
--opt is enabled by default, but can be disabled with --skip-opt.
If you are using a recent copy of the mysqldump program 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> CREATE TABLE t (f DOUBLE);
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`
--
INSERT INTO t VALUES (NULL);
INSERT INTO t VALUES (NULL);
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.
mysqldump supports the following options:
o --help, -?
Display a help message and exit.
o --add-drop-database
Add a DROP DATABASE statement before each CREATE DATABASE statement.
Added in MySQL 4.1.13.
o --add-drop-table
Add a DROP TABLE statement before each CREATE TABLE statement.
o --add-locks
Surround each table dump with LOCK TABLES and UNLOCK TABLES
statements. This results in faster inserts when the dump file is
reloaded. See Section 2.13, "Speed of INSERT Statements".
o --all-databases, -A
Dump all tables in all databases. This is the same as using the
--databases option and naming all the databases on the command line.
o --allow-keywords
Allow creation of column names that are keywords. This works by
prefixing each column name with the table name.
o --comments[={0|1}]
If set to 0, suppresses additional information in the dump file such
as program version, server version, and host. --skip-comments has
the same effect as --comments=0. The default value is 1, which
includes the extra information. Added in MySQL 4.0.17.
o --compact
Produce less verbose output. This option suppresses comments and
enables the --skip-add-drop-table, --no-set-names,
--skip-disable-keys, and --skip-add-locks options. Added in MySQL
4.1.2.
o --compatible=name
Produce output that is more compatible with other database systems
or with older MySQL servers. The value of name can be ansi,
mysql323, mysql40, postgresql, oracle, mssql, db2, maxdb,
no_key_options, no_table_options, or no_field_options. To use
several values, separate them by commas. These values have the same
meaning as the corresponding options for setting the server SQL
mode. See the section called "THE SERVER SQL MODE".
This option does not guarantee compatibility with other servers. It
only enables those SQL mode values that are currently available for
making dump output more compatible. For example, --compatible=oracle
does not map data types to Oracle types or use Oracle comment
syntax.
This option requires a server version of 4.1.0 or higher. With older
servers, it does nothing.
o --complete-insert, -c
Use complete INSERT statements that include column names.
o --compress, -C
Compress all information sent between the client and the server if
both support compression.
o --create-options
Include all MySQL-specific table options in the CREATE TABLE
statements. Before MySQL 4.1.2, use --all instead.
o --databases, -B
Dump several databases. Normally, mysqldump treats 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. CREATE DATABASE and USE statements are included in
the output before each new database.
o --debug[=debug_options], -# [debug_options]
Write a debugging log. The debug_options string is often
'd:t:o,file_name'. The default is 'd:t:o,/tmp/mysqldump.trace'.
o --default-character-set=charset_name
Use charset_name as the default character set. See Section 8.1, "The
Character Set Used for Data and Sorting". If not specified,
mysqldump from MySQL 4.1.2 or later uses utf8, and earlier versions
use latin1.
o --delayed-insert
Write INSERT DELAYED statements rather than INSERT statements.
o --delete-master-logs
On a master replication server, delete the binary logs after
performing the dump operation. This option automatically enables
--first-slave before MySQL 4.1.8 and enables --master-data
thereafter. It was added in MySQL 3.23.57 (for MySQL 3.23) and MySQL
4.0.13 (for MySQL 4.0).
o --disable-keys, -K
For each table, surround the INSERT statements with /*!40000 ALTER
TABLE tbl_name DISABLE KEYS */; and /*!40000 ALTER TABLE tbl_name
ENABLE KEYS */; statements. This makes loading the dump file into a
MySQL 4.0 or newer server faster because the indexes are created
after all rows are inserted. This option is effective for MyISAM
tables only.
o --extended-insert, -e
Use multiple-row INSERT syntax that include several VALUES lists.
This results in a smaller dump file and speeds up inserts when the
file is reloaded.
o --fields-terminated-by=..., --fields-enclosed-by=...,
--fields-optionally-enclosed-by=..., --fields-escaped-by=...,
--lines-terminated-by=...
These options are used with the -T option and have the same meaning
as the corresponding clauses for LOAD DATA INFILE. See Section 2.5,
"LOAD DATA INFILE Syntax".
o --first-slave, -x
Deprecated. Renamed to --lock-all-tables in MySQL 4.1.8.
o --flush-logs, -F
Flush the MySQL server log files before starting the dump. This
option requires the RELOAD privilege. Note that if you use this
option in combination with the --all-databases (or -A) option, the
logs are flushed for each database dumped. The exception is when
using --lock-all-tables or --master-data: In this case, the logs are
flushed only once, corresponding to the moment that all tables are
locked. If you want your dump and the log flush to happen at exactly
the same moment, you should use --flush-logs together with either
--lock-all-tables or --master-data.
o --force, -f
Continue even if an SQL error occurs during a table dump.
o --host=host_name, -h host_name
Dump data from the MySQL server on the given host. The default host
is localhost.
o --hex-blob
Dump binary columns using hexadecimal notation (for example, 'abc'
becomes 0x616263). The affected data types are BINARY, VARBINARY,
and BLOB in MySQL 4.1 and up, and CHAR BINARY, VARCHAR BINARY, and
BLOB in MySQL 4.0. This option was added in MySQL 4.0.23 and 4.1.8.
o --lock-all-tables, -x
Lock all tables across all databases. This is achieved by acquiring
a global read lock for the duration of the whole dump. This option
automatically turns off --single-transaction and --lock-tables.
Added in MySQL 4.1.8.
o --lock-tables, -l
Lock all tables before starting the dump. The tables are locked with
READ LOCAL to allow concurrent inserts in the case of MyISAM tables.
For transactional tables such as InnoDB and BDB,
--single-transaction is a much better option, because it does not
need to lock the tables at all.
Please note that when dumping multiple databases, --lock-tables
locks tables for each database separately. So, this option does not
guarantee that the tables in the dump file are logically consistent
between databases. Tables in different databases may be dumped in
completely different states.
o --master-data[=value]
Write the binary log filename and position to the output. This
option requires the RELOAD privilege and the binary log must be
enabled. If the option value is equal to 1, the position and
filename are written to the dump output in the form of a CHANGE
MASTER statement that makes a slave server start from the correct
position in the master's binary logs if you use this SQL dump of the
master to set up a slave. If the option value is equal to 2, the
CHANGE MASTER statement is written as an SQL comment. This is the
default action if value is omitted. value may be given as of MySQL
4.1.8; before that, do not specify an option value.
The --master-data option turns on --lock-all-tables, unless
--single-transaction also is specified (in which case, a global read
lock is only acquired a short time at the beginning of the dump. See
also the description for --single-transaction. In all cases, any
action on logs happens at the exact moment of the dump. This option
automatically turns off --lock-tables.
o --no-create-db, -n
This option suppresses the CREATE DATABASE statements that are
otherwise included in the output if the --databases or
--all-databases option is given.
o --no-create-info, -t
Do not write CREATE TABLE statements that re-create each dumped
table.
o --no-data, -d
Do not write any row information for the table. This is very useful
if you want to dump only the CREATE TABLE statement for the table.
o --opt
This option is shorthand; it is the same as specifying
--add-drop-table --add-locks --create-options --disable-keys
--extended-insert --lock-tables --quick --set-charset. It should
give you a fast dump operation and produce a dump file that can be
reloaded into a MySQL server quickly.
As of MySQL 4.1, --opt is enabled by default, but can be disabled
with --skip-opt. To disable only certain of the options enabled by
--opt, use their --skip forms; for example, --skip-add-drop-table or
--skip-quick.
o --password[=password], -p[password]
The password to use when connecting to the server. If you use the
short option form (-p), you cannot have a space between the option
and the password. If you omit the password value following the
--password or -p option on the command line, you are prompted for
one.
Specifying a password on the command line should be considered
insecure. See Section 6.6, "Keeping Your Password Secure".
o --port=port_num, -P port_num
The TCP/IP port number to use for the connection.
o --protocol={TCP|SOCKET|PIPE|MEMORY}
The connection protocol to use. Added in MySQL 4.1.
o --quick, -q
This option is useful for dumping large tables. It forces mysqldump
to retrieve rows for a table from the server a row at a time rather
than retrieving the entire row set and buffering it in memory before
writing it out.
o --quote-names, -Q
Quote database, table, and column names within ``' characters. If
the ANSI_QUOTES SQL mode is enabled, names are quoted within `"'
characters. As of MySQL 4.1.1, --quote-names is enabled by default.
It can be disabled with --skip-quote-names, but this option should
be given after any option such as --compatible that may enable
--quote-names.
o --result-file=file, -r file
Direct output to a given file. This option should be used on Windows
to prevent newline `\n' characters from being converted to `\r\n'
carriage return/newline sequences.
o --set-charset
Add SET NAMES default_character_set to the output. This option is
enabled by default. To suppress the SET NAMES statement, use
--skip-set-charset. This option was added in MySQL 4.1.2.
o --single-transaction
This option issues a BEGIN SQL statement before dumping data from
the server. It is useful only with transactional tables such as
InnoDB and BDB, because then it dumps the consistent state of the
database at the time when BEGIN was issued without blocking any
applications.
When using this option, you should keep in mind that only InnoDB
tables are dumped in a consistent state. For example, any MyISAM or
HEAP tables dumped while using this option may still change state.
The --single-transaction option was added in MySQL 4.0.2. This
option is mutually exclusive with the --lock-tables option, because
LOCK TABLES causes any pending transactions to be committed
implicitly.
To dump big tables, you should combine this option with --quick.
o --socket=path, -S path
For connections to localhost, the Unix socket file to use, or, on
Windows, the name of the named pipe to use.
o --skip-comments
See the description for the --comments option.
o --tab=path, -T path
Produce tab-separated data files. For each dumped table, mysqldump
creates a tbl_name.sql file that contains the CREATE TABLE statement
that creates the table, and a tbl_name.txt file that contains its
data. The option value is the directory in which to write the files.
By default, the .txt data files are formatted using tab characters
between column values and a newline at the end of each line. The
format can be specified explicitly using the --fields-xxx and
--lines--xxx options.
Note: This option should be used only when mysqldump is run on the
same machine as the mysqld server. You must have the FILE privilege,
and the server must have permission to write files in the directory
that you specify.
o --tables
Override the --databases or -B option. All name arguments following
the option are regarded as table names.
o --user=user_name, -u user_name
The MySQL username to use when connecting to the server.
o --verbose, -v
Verbose mode. Print more information about what the program does.
o --version, -V
Display version information and exit.
o --where='where_condition', -w 'where_condition'
Dump only rows selected by the given WHERE condition. Note that
quotes around the condition are mandatory if it contains spaces or
other characters that are special to your command interpreter.
Examples:
--where="user='jimf'"
-w"userid>1"
-w"userid<1"
o --xml, -X
Write dump output as well-formed XML.
You can also set the following variables by using --var_name=value
syntax:
o max_allowed_packet
The maximum size of the buffer for client/server communication. The
value of the variable can be up to 16MB before MySQL 4.0, and up to
1GB from MySQL 4.0 on.
o net_buffer_length
The initial size of the buffer for client/server communication. When
creating multiple-row-insert statements (as with option
--extended-insert or --opt), mysqldump creates rows up to
net_buffer_length length. If you increase this variable, you should
also ensure that the net_buffer_length variable in the MySQL server
is at least this large.
It is also possible to set variables by using
--set-variable=var_name=value or -O var_name=value syntax. However,
this syntax is deprecated as of MySQL 4.0.
The most common use of mysqldump is probably for making a backup of an
entire database:
shell> mysqldump --opt db_name > backup-file.sql
You can read 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 --single-transaction > all_databases.sql
This backup just needs to acquire 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 and only if one long updating
statement is running when the FLUSH statement is issued, the MySQL
server may get stalled until that long statement finishes, and then the
dump becomes lock-free. 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 9.4, "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
Or:
shell> mysqldump --all-databases --flush-logs --master-data=2
> all_databases.sql
The simultaneous use of --master-data and --single-transaction works as
of MySQL 4.1.8. It provides a convenient way to make an online backup
suitable for point-in-time recovery if tables are stored in the InnoDB
storage engine.
For more information on making backups, see Section 7.1, "Database
Backups", and Section 7.2.1, "Backup Policy".
SEE ALSO
isamchk(1), isamlog(1), msql2mysql(1), myisamchk(1), myisamlog(1),
myisampack(1), mysql(1), mysql.server(1), mysql_config(1),
mysql_fix_privilege_tables(1), mysql_zap(1), mysqlaccess(1),
mysqladmin(1), mysqlbinlog(1), mysqlcheck(1), mysqld(1),
mysqld_multi(1), mysqld_safe(1), mysqlhotcopy(1), mysqlimport(1),
mysqlshow(1), pack_isam(1), perror(1), replace(1), safe_mysqld(1)
For more information, please refer to the MySQL Reference Manual, which
may already be installed locally and which is also available online at
http://dev.mysql.com/doc/.
AUTHOR
MySQL AB (http://www.mysql.com/). This software comes with no
warranty.
MySQL 4.1 01/27/2006 MYSQLDUMP(1)
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