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.
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.
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.
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:
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:
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.
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:
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”.
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.
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.
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”.
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:
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
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.
–databases or –all-databases option.
To see a list of the options your version of mysqldump supports, issue the command
mysqldump –help.
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”.
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.
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.
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.
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.
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).)
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.
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.
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.
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.
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.
exits.
· –dump-date
If the –comments option is given, mysqldump produces a comment at the end of the
dump of the following form:
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.
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.
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.
takes precedence.
· –log-error=file_name
Log warnings and errors by appending them to the named file. The default is to do
no logging.
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.
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”.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
–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.
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.
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:
│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).
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.
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.
–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”.
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.
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.
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”.
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.
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”.
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.
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.
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.
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.
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.
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.
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.
–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.
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.
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”.)
│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=”
” title=”http://www.w3.org/2001/XMLSchema-instance”>” class=”http”>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>
<?xml version=”1.0″?>
<mysqldump xmlns:xsi=”
” title=”http://www.w3.org/2001/XMLSchema-instance”>” class=”http”>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.
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.
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.
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.
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.
–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.
–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.
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.
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”.
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.
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.
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”.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
(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.
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.
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.
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.
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.
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:
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.
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:
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.
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”.
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.)
–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.
(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”.
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.
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.
Section C.5, “Restrictions on Views” for a workaround.
参考文献
- man 1 mysqldump，version 10.13 Distrib 5.7.16, for linux-glibc2.5 (x86_64)
- MySQL 5.7 Reference Manual/mysqldump: https://dev.mysql.com/doc/refman/5.7/en/mysqldump.html
连接 Connection
MySQL 手册 /mysqldump: https://dev.mysql.com/doc/refman/5.7/en/mysqldump.html#option_mysqldump_routines
mysqldump 命令登录服务器后来获取相关的信息。以下选项指定了如何连接 MySQL 服务器（远程和本地主机）
–login-path=name
指定要使用的已命名的.mylogin.cnf 文件中的「登录路径（login path）」。
「登录路径（login path）」，是一个选项组，该选项组中保存了连接到 MySQL 服务器的登录认证信息。
有关登录路径的内容，参考官方文档：https://dev.mysql.com/doc/mysql-utilities/1.5/en/mysql-utils-intro-connspec-mylogin.cnf.html
如果要创建或者修改「登录路径（login path）」文件，使用 mysql_config_editor 命令。
有关 mysql_config_editor 命令的使用方法可参考文档：https://dev.mysql.com/doc/refman/5.7/en/mysql-config-editor.html
–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, mysqldump prompts for one.
Specifying a password on the command line should be considered insecure. See Section 6.1.2.1, “End-User Guidelines for Password Security”. You can use an option file to avoid giving the password on the command line.
DDL
https://dev.mysql.com/doc/refman/5.7/en/mysqldump.html#mysqldump-ddl-options
–no-create-db, -n
如果给出了–databases或–all-databases选项，使用该选项后不会输出CREATE DATABASE语句。
–no-create-info, -t
不要为每个dump的表输出CREATE TABLE语句。
注意：此选项不会从mysqldump的输出中排除创建「日志文件组」或「tablespace」的语句；但是可以使用–no-tablespaces选项来达到目的。
· –no-tablespaces, -y
This option suppresses all CREATE LOGFILE GROUP and CREATE TABLESPACE statements
in the output of mysqldump.
in the output of mysqldump.
· –replace
Write REPLACE statements rather than INSERT statements.
输出过滤 | Filtering Options
MySQL手册/mysqldump：https://dev.mysql.com/doc/refman/5.7/en/mysqldump.html#mysqldump-filter-options
以下选项控制将哪些类型的对象写入dump文件中：
- 按类别：例如触发器或事件；
- 通过名称::选择要转储的数据库和表；
- 甚至可以使用WHERE子句从表数据中过滤行；
–all-databases, -A
dump所有库中所有表；
等价于使用–databases选项并指定所有的库。
–databases, -B
dump指定的数据库。
通常，mysqldump将命令行上的第一个名称参数视为数据库名称，并将后跟的名称作为表名称。使用此选项，它将所有名称参数视为数据库名称。
输出内容中，会在CREATE TABLE语句前自动输出CREATE DATABASE和USE语句。
此选项可用于dump数据库INFORMATION_SCHEMA和performace_schema，因为默认情况下，即使使用了–all-databases选项也不会dump出来。
（也可以使用–skip-lock-tables选项。）
–events, -E
同时dump出事件计划（即包含CREATE EVENT语句）。需要在对应数据库上具有EVENT权限。
注意：dump的CREATE EVENT语句并不包含时间属性。如果需要原始的时间，需要使用具有权限的MySQL帐户直接dump并重新加载mysql.event表。
–ignore-error=error[,error]…
忽略指定的错误。参数列表为逗号分割的错误号，指定了要忽略的错误。
如果使用了–force选项，–force的优先级要高。
MySQL 5.7.1中添加了该选项。
–ignore-table=db_name.tbl_name
忽略指定的表，参数必须是”库名.表名”的格式。如果要忽略多个表，需要多次使用该选项。同时可以用于忽略视图。
–no-data, -d
不导出表中的数据。
–routines, -R
导出内容中包含存储过程和存储函数（CREATE PROCEDURE与CREATE FUNCTION语句）。需要对mysql.proc具有select权限。
注意：导出的语句中不包含创建及就修改时间戳。如果想保留时间戳，直接使用具有权限的MySQL帐户来dump和重新加载mysql.proc表。
–tables
用于覆盖–databases/-B选项。将该选项指定的所有名字都视为表名。
–triggers
同时dump出表中的trigger，该选项默认使启动的，使用–skip-triggers选项，忽略trigger的导出。
在MySQL 5.7.2之前，一个表不能具有触发事件（INSERT，UPDATE，DELETE）和动作时机（BEFORE，AFTER）相同组合的多个触发器。MySQL 5.7.2提升此限制，允许多个触发器。mysqldump以激活顺序dump触发器，以便在导入dump文件时，以相同的激活顺序创建触发器。但是，如果mysqldump的dump文件中存在同一张表具有相同触发事件和触发时机的多个触发器的情况，那么将dump文件导入旧服务器中时会发生错误。有关解决方法，请参见MySQL文档第2.11.2.1节“影响从MySQL 5.7降级的更改”；可以将触发器转换为与旧服务器兼容。
–where=’where_condition’, -w ‘where_condition’
只dump符合where_condition条件的行。“该用引号的地方”需要使用引号。
Examples:
–where=”user=’jimf'”
-w”userid>1″
-w”userid<1″