「Linux下,mysqldump命令」

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mysqldump,数据库备份程序。mysqldump执行逻辑备份,生成一组可以执行的用于重现原始数据库对象定义和表数据的SQL语句
所以本质上讲是通过生成SQL语句进行备份。

它可以dump一个或多个MySQL数据库,进行备份或传输到另一个SQL服务器。

mysqldump命令还可以生成CSV,其他分隔文本或XML格式的输出。

命令行语法格式

mysqldump [options] [db_name [tbl_name …]]

Note
If you have tables that contain generated columns, use the mysqldump utility
provided with MySQL 5.7.9 or higher to create your dump files. The mysqldump
utility provided in earlier releases uses incorrect syntax for generated column
definitions (Bug #20769542). You can use the INFORMATION_SCHEMA.COLUMNS table to
identify tables with generated columns.

mysqldump requires at least the SELECT privilege for dumped tables, SHOW VIEW for

dumped views, TRIGGER 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.

mysqldump output can include ALTER DATABASE statements that change the database

collation. These may be used when dumping stored programs to preserve their character

encodings. To reload a dump file containing such statements, the ALTER privilege for

the affected database is required.

Note

A dump made using PowerShell on Windows with output redirection creates a file

that has UTF-16 encoding:

shell> mysqldump [options] > dump.sql

However, UTF-16 is not permitted as a connection character set (see

Section 11.1.5, “Connection Character Sets and Collations”), so the dump file will

not load correctly. To work around this issue, use the –result-file option, which

creates the output in ASCII format:

shell> mysqldump [options] –result-file=dump.sql

Performance and Scalability Considerations

mysqldump advantages include the

convenience and flexibility of viewing or even editing the output before restoring.

You can clone databases for development and DBA work, or produce slight variations of

an existing database for testing. It is not intended as a fast or scalable solution

for backing up substantial amounts of data. With large data sizes, even if the backup

step takes a reasonable time, restoring the data can be very slow because replaying

the SQL statements involves disk I/O for insertion, index creation, and so on.

For large-scale backup and restore, a physical backup is more appropriate, to copy the

data files in their original format that can be restored quickly:

· If your tables are primarily InnoDB tables, or if you have a mix of InnoDB and
MyISAM tables, consider using the mysqlbackup command of the MySQL Enterprise

Backup product. (Available as part of the Enterprise subscription.) It provides

the best performance for InnoDB backups with minimal disruption; it can also back

up tables from MyISAM and other storage engines; and it provides a number of

convenient options to accommodate different backup scenarios. See Section 27.2,

“MySQL Enterprise Backup Overview”.

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, use the –skip-opt option instead of the –opt or

–extended-insert option.

For additional information about mysqldump, see Section 8.4, “Using mysqldump for

Backups”.

Invocation Syntax

There are in general three ways to use mysqldump—in

order to dump a set of one or more tables, a set of one or more complete databases, or

an entire MySQL server—as shown here:

shell> mysqldump [options] db_name [tbl_name …]

shell> mysqldump [options] –databases db_name …

shell> mysqldump [options] –all-databases

To dump entire databases, do not name any tables following db_name, or use the

–databases or –all-databases option.

To see a list of the options your version of mysqldump supports, issue the command

mysqldump –help.

Option Syntax – Alphabetical Summary

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 5.2.6, “Using Option Files”.

连接有关的选项(Connection Options)

Option-File Options

These options are used to control which option files to read.

· –defaults-extra-file=file_name

Read this option file after the global option file but (on Unix) before the user

option file. If the file does not exist or is otherwise inaccessible, an error

occurs. file_name is interpreted relative to the current directory if given as a

relative path name rather than a full path name.

· –defaults-file=file_name

Use only the given option file. If the file does not exist or is otherwise

inaccessible, an error occurs. file_name is interpreted relative to the current

directory if given as a relative path name rather than a full path name.

Exception: Even with –defaults-file, client programs read .mylogin.cnf.

· –defaults-group-suffix=str

Read not only the usual option groups, but also groups with the usual names and a

suffix of str. For example, mysqldump normally reads the [client] and [mysqldump]

groups. If the –defaults-group-suffix=_other option is given, mysqldump also

reads the [client_other] and [mysqldump_other] groups.

· –no-defaults

Do not read any option files. If program startup fails due to reading unknown

options from an option file, –no-defaults can be used to prevent them from being

read.

The exception is that the .mylogin.cnf file, if it exists, is read in all cases.

This permits passwords to be specified in a safer way than on the command line

even when –no-defaults is used. (.mylogin.cnf is created by the

mysql_config_editor utility. See mysql_config_editor(1).)

· –print-defaults

Print the program name and all options that it gets from option files.

DDL相关选项(DDL Options)

Debug相关的选项(Debug Options)

The following options print debugging information, encode debugging

information in the dump file, or let the dump operation proceed regardless of

potential problems.

· –allow-keywords

Permit creation of column names that are keywords. This works by prefixing each

column name with the table name.

· –comments, -i

Write additional information in the dump file such as program version, server

version, and host. This option is enabled by default. To suppress this additional

information, use –skip-comments.

· –debug[=debug_options], -# [debug_options]

Write a debugging log. A typical debug_options string is d:t:o,file_name. The

default value is d:t:o,/tmp/mysqldump.trace.

· –debug-check

Print some debugging information when the program exits.

· –debug-info

Print debugging information and memory and CPU usage statistics when the program

exits.

· –dump-date

If the –comments option is given, mysqldump produces a comment at the end of the

dump of the following form:

— Dump completed on DATE

However, the date causes dump files taken at different times to appear to be

different, even if the data are otherwise identical. –dump-date and

–skip-dump-date control whether the date is added to the comment. The default is

–dump-date (include the date in the comment). –skip-dump-date suppresses date

printing.

· –force, -f

Ignore all errors; continue even if an SQL error occurs during a table dump.

One use for this option is to cause mysqldump to continue executing even when it

encounters a view that has become invalid because the definition refers to a table

that has been dropped. Without –force, mysqldump exits with an error message.

With –force, mysqldump prints the error message, but it also writes an SQL

comment containing the view definition to the dump output and continues executing.

If the –ignore-error option is also given to ignore specific errors, –force

takes precedence.

· –log-error=file_name

Log warnings and errors by appending them to the named file. The default is to do

no logging.

· –skip-comments

See the description for the –comments option.

· –verbose, -v

Verbose mode. Print more information about what the program does.

Internationalization Options

The following options change how the mysqldump command

represents character data with national language settings.

· –character-sets-dir=dir_name

The directory where character sets are installed. See Section 11.5, “Character Set

Configuration”.

· –default-character-set=charset_name

Use charset_name as the default character set. See Section 11.5, “Character Set

Configuration”. If no character set is specified, mysqldump uses utf8.

· –no-set-names, -N

Turns off the –set-charset setting, the same as specifying –skip-set-charset.

· –set-charset

Write SET NAMES default_character_set to the output. This option is enabled by

default. To suppress the SET NAMES statement, use –skip-set-charset.

Replication Options

The mysqldump command is frequently used to create an empty

instance, or an instance including data, on a slave server in a replication

configuration. The following options apply to dumping and restoring data on

replication master and slave servers.

· –apply-slave-statements

For a slave dump produced with the –dump-slave option, add a STOP SLAVE statement

before the CHANGE MASTER TO statement and a START SLAVE statement at the end of

the output.

· –delete-master-logs

On a master replication server, delete the binary logs by sending a PURGE BINARY

LOGS statement to the server after performing the dump operation. This option

automatically enables –master-data.

· –dump-slave[=value]

This option is similar to –master-data except that it is used to dump a

replication slave server to produce a dump file that can be used to set up another

server as a slave that has the same master as the dumped server. It causes the

dump output to include a CHANGE MASTER TO statement that indicates the binary log

coordinates (file name and position) of the dumped slave’s master. The CHANGE

MASTER TO statement reads the values of Relay_Master_Log_File and

Exec_Master_Log_Pos from the SHOW SLAVE STATUS output and uses them for

MASTER_LOG_FILE and MASTER_LOG_POS respectively. These are the master server

coordinates from which the slave should start replicating.

Note

Inconsistencies in the sequence of transactions from the relay log which have

been executed can cause the wrong position to be used. See Section 18.4.1.34,

“Replication and Transaction Inconsistencies” for more information.
–dump-slave causes the coordinates from the master to be used rather than those

of the dumped server, as is done by the –master-data option. In addition,

specfiying this option causes the –master-data option to be overridden, if used,

and effectively ignored.

Warning

This option should not be used if the server where the dump is going to be

applied uses gtid_mode=ON and MASTER_AUTOPOSITION=1.
The option value is handled the same way as for –master-data (setting no value or

1 causes a CHANGE MASTER TO statement to be written to the dump, setting 2 causes

the statement to be written but encased in SQL comments) and has the same effect

as –master-data in terms of enabling or disabling other options and in how

locking is handled.

This option causes mysqldump to stop the slave SQL thread before the dump and

restart it again after.

In conjunction with –dump-slave, the –apply-slave-statements and

–include-master-host-port options can also be used.

· –include-master-host-port

For the CHANGE MASTER TO statement in a slave dump produced with the –dump-slave

option, add MASTER_HOST and MASTER_PORT options for the host name and TCP/IP port

number of the slave’s master.

· –master-data[=value]

Use this option to dump a master replication server to produce a dump file that

can be used to set up another server as a slave of the master. It causes the dump

output to include a CHANGE MASTER TO statement that indicates the binary log

coordinates (file name and position) of the dumped server. These are the master

server coordinates from which the slave should start replicating after you load

the dump file into the slave.

If the option value is 2, the CHANGE MASTER TO statement is written as an SQL

comment, and thus is informative only; it has no effect when the dump file is

reloaded. If the option value is 1, the statement is not written as a comment and

takes effect when the dump file is reloaded. If no option value is specified, the

default value is 1.

This option requires the RELOAD privilege and the binary log must be enabled.

The –master-data option automatically turns off –lock-tables. It also turns on

–lock-all-tables, unless –single-transaction also is specified, in which case, a

global read lock is acquired only for a short time at the beginning of the dump

(see the description for –single-transaction). In all cases, any action on logs

happens at the exact moment of the dump.

It is also possible to set up a slave by dumping an existing slave of the master,

using the –dump-slave option, which overrides –master-data and causes it to be

ignored if both options are used.

· –set-gtid-purged=value

This option enables control over global transaction ID (GTID) information written

to the dump file, by indicating whether to add a SET @@global.gtid_purged

statement to the output. This option may also cause a statement to be written to

the output that disables binary logging while the dump file is being reloaded.

The following table shows the permitted option values. The default value is AUTO.

┌──────┬────────────────────────────────┐

│Value │ Meaning │

├──────┼────────────────────────────────┤

│OFF │ Add no SET statement to the │

│ │ output. │

├──────┼────────────────────────────────┤

│ON │ Add a SET statement to the │

│ │ output. An error occurs if │

│ │ GTIDs are │

│ │ not enabled on the server. │

├──────┼────────────────────────────────┤

│AUTO │ Add a SET statement to the │

│ │ output if GTIDs are │

│ │ enabled on │

│ │ the server. │

└──────┴────────────────────────────────┘

The –set-gtid-purged option has the following effect on binary logging when the

dump file is reloaded:

· –set-gtid-purged=OFF: SET @@SESSION.SQL_LOG_BIN=0; is not added to the
output.

· –set-gtid-purged=ON: SET @@SESSION.SQL_LOG_BIN=0; is added to the output.

· –set-gtid-purged=AUTO: SET @@SESSION.SQL_LOG_BIN=0; is added to the output if
GTIDs are enabled on the server you are backing up (that is, if AUTO evaluates

to ON).

Format Options

The following options specify how to represent the entire dump file

or certain kinds of data in the dump file. They also control whether certain optional

information is written to the dump file.

· –compact

Produce more compact output. This option enables the –skip-add-drop-table,

–skip-add-locks, –skip-comments, –skip-disable-keys, and –skip-set-charset

options.

· –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 Section 6.1.8,

“Server SQL Modes”.

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.

· –complete-insert, -c

Use complete INSERT statements that include column names.

· –create-options

Include all MySQL-specific table options in the CREATE TABLE statements.

· –fields-terminated-by=…, –fields-enclosed-by=…,
–fields-optionally-enclosed-by=…, –fields-escaped-by=…

These options are used with the –tab option and have the same meaning as the

corresponding FIELDS clauses for LOAD DATA INFILE. See Section 14.2.6, “LOAD DATA

INFILE Syntax”.

· –hex-blob

Dump binary columns using hexadecimal notation (for example, ‘abc’ becomes

0x616263). The affected data types are BINARY, VARBINARY, the BLOB types, and BIT.

· –lines-terminated-by=…

This option is used with the –tab option and has the same meaning as the

corresponding LINES clause for LOAD DATA INFILE. See Section 14.2.6, “LOAD DATA

INFILE Syntax”.

· –quote-names, -Q

Quote identifiers (such as database, table, and column names) within “`”

characters. If the ANSI_QUOTES SQL mode is enabled, identifiers are quoted within

“”” characters. This option 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.

· –result-file=file_name, -r file_name

Direct output to the named file. The result file is created and its previous

contents overwritten, even if an error occurs while generating the dump.

This option should be used on Windows to prevent newline “\n” characters from

being converted to “\r\n” carriage return/newline sequences.

· –tab=dir_name, -T dir_name

Produce tab-separated text-format data files. For each dumped table, mysqldump

creates a tbl_name.sql file that contains the CREATE TABLE statement that creates

the table, and the server writes a tbl_name.txt file that contains its data. The

option value is the directory in which to write the files.

Note

This option should be used only when mysqldump is run on the same machine as

the mysqld server. Because the server creates files *.txt file in the

directory that you specify, the directory must be writable by the server and

the MySQL account that you use must have the FILE privilege. Because mysqldump

creates *.sql in the same directory, it must be writable by your system login

account.
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-terminated-by options.

Column values are converted to the character set specified by the

–default-character-set option.

· –tz-utc

This option enables TIMESTAMP columns to be dumped and reloaded between servers in

different time zones. mysqldump sets its connection time zone to UTC and adds SET

TIME_ZONE=’+00:00′ to the dump file. Without this option, TIMESTAMP columns are

dumped and reloaded in the time zones local to the source and destination servers,

which can cause the values to change if the servers are in different time zones.

–tz-utc also protects against changes due to daylight saving time. –tz-utc is

enabled by default. To disable it, use –skip-tz-utc.

· –xml, -X

Write dump output as well-formed XML.

NULL, ‘NULL’, and Empty Values: For a column named column_name, the NULL value, an

empty string, and the string value ‘NULL’ are distinguished from one another in

the output generated by this option as follows.

┌──────────────────────┬─────────────────────────────────┐

│Value: │ XML Representation: │

├──────────────────────┼─────────────────────────────────┤

│NULL (unknown value) │ <field name=”column_name” │

│ │ xsi:nil=”true” /> │

├──────────────────────┼─────────────────────────────────┤

│” (empty string) │ <field │

│ │ name=”column_name”></field> │

├──────────────────────┼─────────────────────────────────┤

│’NULL’ (string value) │ <field │

│ │ name=”column_name”>NULL</field> │

└──────────────────────┴─────────────────────────────────┘

The output from the mysql client when run using the –xml option also follows the

preceding rules. (See the section called “MYSQL OPTIONS”.)

XML output from mysqldump includes the XML namespace, as shown here:

shell> mysqldump –xml -u root world City

<?xml version=”1.0″?>

<mysqldump xmlns:xsi=”
http://www.w3.org/2001/XMLSchema-instance“>

<database name=”world”>

<table_structure name=”City”>

<field Field=”ID” Type=”int(11)” Null=”NO” Key=”PRI” Extra=”auto_increment” />

<field Field=”Name” Type=”char(35)” Null=”NO” Key=”” Default=”” Extra=”” />

<field Field=”CountryCode” Type=”char(3)” Null=”NO” Key=”” Default=”” Extra=”” />

<field Field=”District” Type=”char(20)” Null=”NO” Key=”” Default=”” Extra=”” />

<field Field=”Population” Type=”int(11)” Null=”NO” Key=”” Default=”0″ Extra=”” />

<key Table=”City” Non_unique=”0″ Key_name=”PRIMARY” Seq_in_index=”1″ Column_name=”ID”

Collation=”A” Cardinality=”4079″ Null=”” Index_type=”BTREE” Comment=”” />

<options Name=”City” Engine=”MyISAM” Version=”10″ Row_format=”Fixed” Rows=”4079″

Avg_row_length=”67″ Data_length=”273293″ Max_data_length=”18858823439613951″

Index_length=”43008″ Data_free=”0″ Auto_increment=”4080″

Create_time=”2007-03-31 01:47:01″ Update_time=”2007-03-31 01:47:02″

Collation=”latin1_swedish_ci” Create_options=”” Comment=”” />

</table_structure>

<table_data name=”City”>

<row>

<field name=”ID”>1</field>

<field name=”Name”>Kabul</field>

<field name=”CountryCode”>AFG</field>

<field name=”District”>Kabol</field>

<field name=”Population”>1780000</field>

</row>



<row>

<field name=”ID”>4079</field>

<field name=”Name”>Rafah</field>

<field name=”CountryCode”>PSE</field>

<field name=”District”>Rafah</field>

<field name=”Population”>92020</field>

</row>

</table_data>

</database>

</mysqldump>

过滤选项(Filtering Options)

Performance Options

The following options are the most relevant for the performance

particularly of the restore operations. For large data sets, restore operation

(processing the INSERT statements in the dump file) is the most time-consuming part.

When it is urgent to restore data quickly, plan and test the performance of this stage

in advance. For restore times measured in hours, you might prefer an alternative

backup and restore solution, such as MySQL Enterprise Backup for InnoDB-only and

mixed-use databases.

Performance is also affected by the transactional options, primarily for the dump

operation.

· –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 faster because the indexes are created after all

rows are inserted. This option is effective only for nonunique indexes of MyISAM

tables.

· –extended-insert, -e

Write INSERT statements using multiple-row syntax that includes several VALUES

lists. This results in a smaller dump file and speeds up inserts when the file is

reloaded.

· –insert-ignore

Write INSERT IGNORE statements rather than INSERT statements.

· –opt

This option, enabled by default, is shorthand for the combination of

–add-drop-table –add-locks –create-options –disable-keys –extended-insert

–lock-tables –quick –set-charset. It gives a fast dump operation and produces a

dump file that can be reloaded into a MySQL server quickly.

Because the –opt option is enabled by default, you only specify its converse, the

–skip-opt to turn off several default settings. See the discussion of mysqldump

option groups for information about selectively enabling or disabling a subset of

the options affected by –opt.

· –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.

· –skip-opt

See the description for the –opt option.

Transactional Options

The following options trade off the performance of the dump

operation, against the reliability and consistency of the exported data.

· –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 9.2.2.1,

“Speed of INSERT Statements”.

· –flush-logs, -F

Flush the MySQL server log files before starting the dump. This option requires

the RELOAD privilege. If you use this option in combination with the

–all-databases option, the logs are flushed for each database dumped. The

exception is when using –lock-all-tables, –master-data, or –single-transaction:

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 –lock-all-tables,

–master-data, or –single-transaction.

· –flush-privileges

Add a FLUSH PRIVILEGES statement to the dump output after dumping the mysql

database. This option should be used any time the dump contains the mysql database

and any other database that depends on the data in the mysql database for proper

restoration.

Note

For upgrades to MySQL 5.7.2 or higher from older versions, do not use

–flush-privileges. For upgrade instructions in this case, see

Section 2.11.1.1, “Changes Affecting Upgrades to MySQL 5.7”.

· –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.

· –lock-tables, -l

For each dumped database, lock all tables to be dumped before dumping them. The

tables are locked with READ LOCAL to permit concurrent inserts in the case of

MyISAM tables. For transactional tables such as InnoDB, –single-transaction is a

much better option than –lock-tables because it does not need to lock the tables

at all.

Because –lock-tables locks tables for each database separately, 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.

Some options, such as –opt, automatically enable –lock-tables. If you want to

override this, use –skip-lock-tables at the end of the option list.

· –no-autocommit

Enclose the INSERT statements for each dumped table within SET autocommit = 0 and

COMMIT statements.

· –order-by-primary

Dump each table’s rows sorted by its primary key, or by its first unique index, if

such an index exists. This is useful when dumping a MyISAM table to be loaded into

an InnoDB table, but makes the dump operation take considerably longer.

· –shared-memory-base-name=name

On Windows, the shared-memory name to use, for connections made using shared

memory to a local server. The default value is MYSQL. The shared-memory name is

case sensitive.

The server must be started with the –shared-memory option to enable shared-memory

connections.

· –single-transaction

This option sets the transaction isolation mode to REPEATABLE READ and sends a

START TRANSACTION SQL statement to the server before dumping data. It is useful

only with transactional tables such as InnoDB, because then it dumps the

consistent state of the database at the time when START TRANSACTION 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 MEMORY tables dumped while using

this option may still change state.

While a –single-transaction dump is in process, to ensure a valid dump file

(correct table contents and binary log coordinates), no other connection should

use the following statements: ALTER TABLE, CREATE TABLE, DROP TABLE, RENAME TABLE,

TRUNCATE TABLE. A consistent read is not isolated from those statements, so use of

them on a table to be dumped can cause the SELECT that is performed by mysqldump

to retrieve the table contents to obtain incorrect contents or fail.

The –single-transaction option and the –lock-tables option are mutually

exclusive because LOCK TABLES causes any pending transactions to be committed

implicitly.

To dump large tables, combine the –single-transaction option with the –quick

option.

Help Options

–help, -?
显示帮助信息。

–version, -V
显示版本信息。

Option Groups

· The –opt option turns on several settings that work together to perform a fast
dump operation. All of these settings are on by default, because –opt is on by

default. Thus you rarely if ever specify –opt. Instead, you can turn these

settings off as a group by specifying –skip-opt, the optionally re-enable certain

settings by specifying the associated options later on the command line.

· The –compact option turns off several settings that control whether optional
statements and comments appear in the output. Again, you can follow this option

with other options that re-enable certain settings, or turn all the settings on by

using the –skip-compact form.

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.

示例(Examples)

To make a backup of an entire database:

shell> mysqldump db_name > backup-file.sql

To load the dump file back into the server:

shell> mysql db_name < backup-file.sql

Another way to reload the dump file:

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

You can 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 6.4.4, “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 –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 8.2, “Database Backup Methods”,

and Section 8.3, “Example Backup and Recovery Strategy”.

· To select the effect of –opt except for some features, use the –skip option for
each feature. To disable extended inserts and memory buffering, use –opt

–skip-extended-insert –skip-quick. (Actually, –skip-extended-insert

–skip-quick is sufficient because –opt is on by default.)

· To reverse –opt for all features except index disabling and table locking, use
–skip-opt –disable-keys –lock-tables.

存在的限制(Restrictions)

mysqldump does not dump the INFORMATION_SCHEMA, performance_schema, or

(as of MySQL 5.7.8) sys schema by default. To dump any of these, name them explicitly

on the command line. You can also name them with the –databases option. For

INFORMATION_SCHEMA and performance_schema, also use the –skip-lock-tables option.

mysqldump does not dump the MySQL Cluster ndbinfo information database.

It is not recommended to restore from a dump made using mysqldump to a MySQL 5.6.9 or

earlier server that has GTIDs enabled. See Section 18.1.3.4, “Restrictions on

Replication with GTIDs”.

mysqldump includes statements to recreate the general_log and slow_query_log tables

for dumps of the mysql database. Log table contents are not dumped.

If you encounter problems backing up views due to insufficient privileges, see

Section C.5, “Restrictions on Views” for a workaround.

参考文献