mysqldump 是MySQL的一個命令列工具，用於邏輯備份。可以將資料庫和表的結構，以及表中的資料分別匯出成：create database, create table, insert into的sql語句。當然也可以匯出 儲存過程，觸發器，函式，排程事件(events)。不管是程式設計師，還是DBA都會經常使用的一個工具。

1. mysqldump --help

mysqldump 的選項很多，我們看一下他的幫助文件：

mysqldump  Ver 10.13 Distrib 5.6.26, for linux-glibc2.5 (i686)
Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Dumping structure and contents of MySQL databases and tables.
Usage: mysqldump [OPTIONS] database [tables]
OR     mysqldump [OPTIONS] --databases [OPTIONS] DB1 [DB2 DB3...]
OR     mysqldump [OPTIONS] --all-databases [OPTIONS]

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf /usr/local/mysql/etc/my.cnf ~/.my.cnf 
The following groups are read: mysqldump client
The following options may be given as the first argument:
--print-defaults        Print the program argument list and exit.
--no-defaults           Don't read default options from any option file,
                        except for login file.
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
                        Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.
  -A, --all-databases Dump all the databases. This will be same as --databases
                      with all databases selected.
  -Y, --all-tablespaces 
                      Dump all the tablespaces.
  -y, --no-tablespaces 
                      Do not dump any tablespace information.
  --add-drop-database Add a DROP DATABASE before each create.
  --add-drop-table    Add a DROP TABLE before each create.
                      (Defaults to on; use --skip-add-drop-table to disable.)
  --add-drop-trigger  Add a DROP TRIGGER before each create.
  --add-locks         Add locks around INSERT statements.
                      (Defaults to on; use --skip-add-locks to disable.)
  --allow-keywords    Allow creation of column names that are keywords.
  --apply-slave-statements 
                      Adds 'STOP SLAVE' prior to 'CHANGE MASTER' and 'START
                      SLAVE' to bottom of dump.
  --bind-address=name IP address to bind to.
  --character-sets-dir=name 
                      Directory for character set files.
  -i, --comments      Write additional information.
                      (Defaults to on; use --skip-comments to disable.)
  --compatible=name   Change the dump to be compatible with a given mode. By
                      default tables are dumped in a format optimized for
                      MySQL. Legal modes are: ansi, mysql323, mysql40,
                      postgresql, oracle, mssql, db2, maxdb, no_key_options,
                      no_table_options, no_field_options. One can use several
                      modes separated by commas. Note: Requires MySQL server
                      version 4.1.0 or higher. This option is ignored with
                      earlier server versions.
  --compact           Give less verbose output (useful for debugging). Disables
                      structure comments and header/footer constructs.  Enables
                      options --skip-add-drop-table --skip-add-locks
                      --skip-comments --skip-disable-keys --skip-set-charset.
  -c, --complete-insert 
                      Use complete insert statements.
  -C, --compress      Use compression in server/client protocol.
  -a, --create-options 
                      Include all MySQL specific create options.
                      (Defaults to on; use --skip-create-options to disable.)
  -B, --databases     Dump several databases. Note the difference in usage; in
                      this case no tables are given. All name arguments are
                      regarded as database names. 'USE db_name;' will be
                      included in the output.
  -#, --debug[=#]     This is a non-debug version. Catch this and exit.
  --debug-check       Check memory and open file usage at exit.
  --debug-info        Print some debug info at exit.
  --default-character-set=name 
                      Set the default character set.
  --delayed-insert    Insert rows with INSERT DELAYED.
  --delete-master-logs 
                      Delete logs on master after backup. This automatically
                      enables --master-data.
  -K, --disable-keys  '/*!40000 ALTER TABLE tb_name DISABLE KEYS */; and
                      '/*!40000 ALTER TABLE tb_name ENABLE KEYS */; will be put
                      in the output.
                      (Defaults to on; use --skip-disable-keys to disable.)
  --dump-slave[=#]    This causes the binary log position and filename of the
                      master to be appended to the dumped data output. Setting
                      the value to 1, will printit as a CHANGE MASTER command
                      in the dumped data output; if equal to 2, that command
                      will be prefixed with a comment symbol. This option will
                      turn --lock-all-tables on, unless --single-transaction is
                      specified too (in which case a global read lock is only
                      taken a short time at the beginning of the dump - don't
                      forget to read about --single-transaction below). In all
                      cases any action on logs will happen at the exact moment
                      of the dump.Option automatically turns --lock-tables off.
  -E, --events        Dump events.
  -e, --extended-insert 
                      Use multiple-row INSERT syntax that include several
                      VALUES lists.
                      (Defaults to on; use --skip-extended-insert to disable.)
  --fields-terminated-by=name 
                      Fields in the output file are terminated by the given
                      string.
  --fields-enclosed-by=name 
                      Fields in the output file are enclosed by the given
                      character.
  --fields-optionally-enclosed-by=name 
                      Fields in the output file are optionally enclosed by the
                      given character.
  --fields-escaped-by=name 
                      Fields in the output file are escaped by the given
                      character.
  -F, --flush-logs    Flush logs file in server before starting dump. Note that
                      if you dump many databases at once (using the option
                      --databases= or --all-databases), the logs will be
                      flushed for each database dumped. The exception is when
                      using --lock-all-tables or --master-data: in this case
                      the logs will be flushed only once, corresponding to the
                      moment all tables are locked. So if you want your dump
                      and the log flush to happen at the same exact moment you
                      should use --lock-all-tables or --master-data with
                      --flush-logs.
  --flush-privileges  Emit a FLUSH PRIVILEGES statement 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
                      restore. 
  -f, --force         Continue even if we get an SQL error.
  -?, --help          Display this help message and exit.
  --hex-blob          Dump binary strings (BINARY, VARBINARY, BLOB) in
                      hexadecimal format.
  -h, --host=name     Connect to host.
  --ignore-table=name Do not dump the specified table. To specify more than one
                      table to ignore, use the directive multiple times, once
                      for each table.  Each table must be specified with both
                      database and table names, e.g.,
                      --ignore-table=database.table.
  --include-master-host-port 
                      Adds 'MASTER_HOST=<host>, MASTER_PORT=<port>' to 'CHANGE
                      MASTER TO..' in dump produced with --dump-slave.
  --insert-ignore     Insert rows with INSERT IGNORE.
  --lines-terminated-by=name 
                      Lines in the output file are terminated by the given
                      string.
  -x, --lock-all-tables 
                      Locks all tables across all databases. This is achieved
                      by taking a global read lock for the duration of the
                      whole dump. Automatically turns --single-transaction and
                      --lock-tables off.
  -l, --lock-tables   Lock all tables for read.
                      (Defaults to on; use --skip-lock-tables to disable.)
  --log-error=name    Append warnings and errors to given file.
  --master-data[=#]   This causes the binary log position and filename to be
                      appended to the output. If equal to 1, will print it as a
                      CHANGE MASTER command; if equal to 2, that command will
                      be prefixed with a comment symbol. This option will turn
                      --lock-all-tables on, unless --single-transaction is
                      specified too (in which case a global read lock is only
                      taken a short time at the beginning of the dump; don't
                      forget to read about --single-transaction below). In all
                      cases, any action on logs will happen at the exact moment
                      of the dump. Option automatically turns --lock-tables
                      off.
  --max-allowed-packet=# 
                      The maximum packet length to send to or receive from
                      server.
  --net-buffer-length=# 
                      The buffer size for TCP/IP and socket communication.
  --no-autocommit     Wrap tables with autocommit/commit statements.
  -n, --no-create-db  Suppress the CREATE DATABASE ... IF EXISTS statement that
                      normally is output for each dumped database if
                      --all-databases or --databases is given.
  -t, --no-create-info 
                      Don't write table creation info.
  -d, --no-data       No row information.
  -N, --no-set-names  Same as --skip-set-charset.
  --opt               Same as --add-drop-table, --add-locks, --create-options,
                      --quick, --extended-insert, --lock-tables, --set-charset,
                      and --disable-keys. Enabled by default, disable with
                      --skip-opt.
  --order-by-primary  Sorts each table's rows by primary key, or first unique
                      key, if such a key exists.  Useful when dumping a MyISAM
                      table to be loaded into an InnoDB table, but will make
                      the dump itself take considerably longer.
  -p, --password[=name] 
                      Password to use when connecting to server. If password is
                      not given it's solicited on the tty.
  -P, --port=#        Port number to use for connection.
  --protocol=name     The protocol to use for connection (tcp, socket, pipe,
                      memory).
  -q, --quick         Don't buffer query, dump directly to stdout.
                      (Defaults to on; use --skip-quick to disable.)
  -Q, --quote-names   Quote table and column names with backticks (`).
                      (Defaults to on; use --skip-quote-names to disable.)
  --replace           Use REPLACE INTO instead of INSERT INTO.
  -r, --result-file=name 
                      Direct output to a given file. This option should be used
                      in systems (e.g., DOS, Windows) that use carriage-return
                      linefeed pairs (\r\n) to separate text lines. This option
                      ensures that only a single newline is used.
  -R, --routines      Dump stored routines (functions and procedures).
  --set-charset       Add 'SET NAMES default_character_set' to the output.
                      (Defaults to on; use --skip-set-charset to disable.)
  --set-gtid-purged[=name] 
                      Add 'SET @@GLOBAL.GTID_PURGED' to the output. Possible
                      values for this option are ON, OFF and AUTO. If ON is
                      used and GTIDs are not enabled on the server, an error is
                      generated. If OFF is used, this option does nothing. If
                      AUTO is used and GTIDs are enabled on the server, 'SET
                      @@GLOBAL.GTID_PURGED' is added to the output. If GTIDs
                      are disabled, AUTO does nothing. If no value is supplied
                      then the default (AUTO) value will be considered.
  --single-transaction 
                      Creates a consistent snapshot by dumping all tables in a
                      single transaction. Works ONLY for tables stored in
                      storage engines which support multiversioning (currently
                      only InnoDB does); the dump is NOT guaranteed to be
                      consistent for other storage engines. While a
                      --single-transaction dump is in process, to ensure a
                      valid dump file (correct table contents and binary log
                      position), no other connection should use the following
                      statements: ALTER TABLE, DROP TABLE, RENAME TABLE,
                      TRUNCATE TABLE, as consistent snapshot is not isolated
                      from them. Option automatically turns off --lock-tables.
  --dump-date         Put a dump date to the end of the output.
                      (Defaults to on; use --skip-dump-date to disable.)
  --skip-opt          Disable --opt. Disables --add-drop-table, --add-locks,
                      --create-options, --quick, --extended-insert,
                      --lock-tables, --set-charset, and --disable-keys.
  -S, --socket=name   The socket file to use for connection.
  --secure-auth       Refuse client connecting to server if it uses old
                      (pre-4.1.1) protocol.
                      (Defaults to on; use --skip-secure-auth to disable.)
  --ssl               Enable SSL for connection (automatically enabled with
                      other flags).
  --ssl-ca=name       CA file in PEM format (check OpenSSL docs, implies
                      --ssl).
  --ssl-capath=name   CA directory (check OpenSSL docs, implies --ssl).
  --ssl-cert=name     X509 cert in PEM format (implies --ssl).
  --ssl-cipher=name   SSL cipher to use (implies --ssl).
  --ssl-key=name      X509 key in PEM format (implies --ssl).
  --ssl-crl=name      Certificate revocation list (implies --ssl).
  --ssl-crlpath=name  Certificate revocation list path (implies --ssl).
  --ssl-verify-server-cert 
                      Verify server's "Common Name" in its cert against
                      hostname used when connecting. This option is disabled by
                      default.
  -T, --tab=name      Create tab-separated textfile for each table to given
                      path. (Create .sql and .txt files.) NOTE: This only works
                      if mysqldump is run on the same machine as the mysqld
                      server.
  --tables            Overrides option --databases (-B).
  --triggers          Dump triggers for each dumped table.
                      (Defaults to on; use --skip-triggers to disable.)
  --tz-utc            SET TIME_ZONE='+00:00' at top of dump to allow dumping of
                      TIMESTAMP data when a server has data in different time
                      zones or data is being moved between servers with
                      different time zones.
                      (Defaults to on; use --skip-tz-utc to disable.)
  -u, --user=name     User for login if not current user.
  -v, --verbose       Print info about the various stages.
  -V, --version       Output version information and exit.
  -w, --where=name    Dump only selected records. Quotes are mandatory.
  -X, --xml           Dump a database as well formed XML.
  --plugin-dir=name   Directory for client-side plugins.
  --default-auth=name Default authentication client-side plugin to use.

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
all-databases                     FALSE
all-tablespaces                   FALSE
no-tablespaces                    FALSE
add-drop-database                 FALSE
add-drop-table                    TRUE
add-drop-trigger                  FALSE
add-locks                         TRUE
allow-keywords                    FALSE
apply-slave-statements            FALSE
bind-address                      (No default value)
character-sets-dir                (No default value)
comments                          TRUE
compatible                        (No default value)
compact                           FALSE
complete-insert                   FALSE
compress                          FALSE
create-options                    TRUE
databases                         FALSE
debug-check                       FALSE
debug-info                        FALSE
default-character-set             utf8
delayed-insert                    FALSE
delete-master-logs                FALSE
disable-keys                      TRUE
dump-slave                        0
events                            FALSE
extended-insert                   TRUE
fields-terminated-by              (No default value)
fields-enclosed-by                (No default value)
fields-optionally-enclosed-by     (No default value)
fields-escaped-by                 (No default value)
flush-logs                        FALSE
flush-privileges                  FALSE
force                             FALSE
hex-blob                          FALSE
host                              (No default value)
include-master-host-port          FALSE
insert-ignore                     FALSE
lines-terminated-by               (No default value)
lock-all-tables                   FALSE
lock-tables                       TRUE
log-error                         (No default value)
master-data                       0
max-allowed-packet                25165824
net-buffer-length                 1046528
no-autocommit                     FALSE
no-create-db                      FALSE
no-create-info                    FALSE
no-data                           FALSE
order-by-primary                  FALSE
port                              0
quick                             TRUE
quote-names                       TRUE
replace                           FALSE
routines                          FALSE
set-charset                       TRUE
single-transaction                FALSE
dump-date                         TRUE
socket                            /var/lib/mysql/mysql.sock
secure-auth                       TRUE
ssl                               FALSE
ssl-ca                            (No default value)
ssl-capath                        (No default value)
ssl-cert                          (No default value)
ssl-cipher                        (No default value)
ssl-key                           (No default value)
ssl-crl                           (No default value)
ssl-crlpath                       (No default value)
ssl-verify-server-cert            FALSE
tab                               (No default value)
triggers                          TRUE
tz-utc                            TRUE
user                              (No default value)
verbose                           FALSE
where                             (No default value)
plugin-dir                        (No default value)
default-auth                      (No default value)

mysqldump --help
 

總體看來，幫助文件分成了兩個部分。前一個部分是對各種選項的說明，後一個部分是mysqldump的各種選項的預設值。

mysqldump擁有超多的選項，這樣說明它很靈活，功能強大。為了好理解，可以將他的眾多的選項和引數，根據他們的功能分為幾個類別來介紹。

在此之前，我們還要搞清楚mysqldump的所有的預設選項的值，它們的含義。

2. mysqldump 預設選項：

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
all-databases                     FALSE
all-tablespaces                   FALSE
no-tablespaces                    FALSE
add-drop-database                 FALSE
add-drop-table                    TRUE
add-drop-trigger                  FALSE
add-locks                         TRUE
allow-keywords                    FALSE
apply-slave-statements            FALSE
bind-address                      (No default value)
character-sets-dir                (No default value)
comments                          TRUE
compatible                        (No default value)
compact                           FALSE
complete-insert                   FALSE
compress                          FALSE
create-options                    TRUE
databases                         FALSE
debug-check                       FALSE
debug-info                        FALSE
default-character-set             utf8
delayed-insert                    FALSE
delete-master-logs                FALSE
disable-keys                      TRUE
dump-slave                        0
events                            FALSE
extended-insert                   TRUE
fields-terminated-by              (No default value)
fields-enclosed-by                (No default value)
fields-optionally-enclosed-by     (No default value)
fields-escaped-by                 (No default value)
flush-logs                        FALSE
flush-privileges                  FALSE
force                             FALSE
hex-blob                          FALSE
host                              (No default value)
include-master-host-port          FALSE
insert-ignore                     FALSE
lines-terminated-by               (No default value)
lock-all-tables                   FALSE
lock-tables                       TRUE
log-error                         (No default value)
master-data                       0
max-allowed-packet                25165824
net-buffer-length                 1046528
no-autocommit                     FALSE
no-create-db                      FALSE
no-create-info                    FALSE
no-data                           FALSE
order-by-primary                  FALSE
port                              0
quick                             TRUE
quote-names                       TRUE
replace                           FALSE
routines                          FALSE
set-charset                       TRUE
single-transaction                FALSE
dump-date                         TRUE
socket                            /var/lib/mysql/mysql.sock
secure-auth                       TRUE
ssl                               FALSE
ssl-ca                            (No default value)
ssl-capath                        (No default value)
ssl-cert                          (No default value)
ssl-cipher                        (No default value)
ssl-key                           (No default value)
ssl-crl                           (No default value)
ssl-crlpath                       (No default value)
ssl-verify-server-cert            FALSE
tab                               (No default value)
triggers                          TRUE
tz-utc                            TRUE
user                              (No default value)
verbose                           FALSE
where                             (No default value)
plugin-dir                        (No default value)
default-auth                      (No default value)

mysqldump
 

這些預設值，有的是 false, 有的是 true，有的沒有預設值。

我們要關注的是 預設為 true，也就是 mysqldump 預設給我開啟的選擇，它們的具體含義如下：

add-drop-table                    TRUE 表示在生成表結構語句之前，生成對應的 DROP TABLE IF EXISTS `table_name`; 語句
add-locks                         TRUE 表示在生成表中資料的 insert into `table_name` values(...) 之前生成 LOCK TABLES `tab` WRITE;語句
comments                          TRUE 表示生成備註，就是所有 -- 開頭的說明，比如：-- Dumping data for  for table `tab`. 最好還是啟用；
create-options                    TRUE 表示在生成表結構時會生成：ENGINE=InnoDB AUTO_INCREMENT=827 DEFAULT CHARSET=utf8; 附加建表選項
default-character-set             utf8 指定語句：/*!40101 SET NAMES utf8 */;中的字符集；可能你需要改成 --default-character-set=utf8mb4
disable-keys                      TRUE 表示生產 insert 語句之前，生成：/*!40000 ALTER TABLE `tbl` DISABLE KEYS */; 可以加快insert速度；
extended-insert                   TRUE 表示生產的insert是insert into `tbl` values(...),(...),資料行按照net-buffer-length分割合併成多個batch insert
lock-tables                       TRUE 表示在匯出的過程中會鎖定所有表；
max-allowed-packet                25165824 最大支援 24M 的資料包；
net-buffer-length                 1046528  1M大小的socket buffer
quick                             TRUE 表示在匯出語句時，不快取，直接輸出到控制檯或者檔案中；
quote-names                       TRUE 表示對錶名和列名使用 `` 符號包裹；防止它們是關鍵字時會出錯;
set-charset                       TRUE default-character-set=utf8指定字符集，而--set-charset=1/0 表示是否生成/*!40101 SET NAMES utf8 */; 
dump-date                         TRUE 表示是否在匯出檔案的末尾生成匯出時間：-- Dump completed on 2015-09-15 11:15:10 
secure-auth                       TRUE 表示登入判斷密碼時使用新的加密演算法，拒絕就的加密演算法
triggers                          TRUE 表示生成觸發器指令碼；
tz-utc                            TRUE 表示是否生成：/*!40103 SET @
 
[email protected]@TIME_ZONE */; /*!40103 SET TIME_ZONE='+00:00' */;

如果要關閉這些開啟的預設選項時，需要明確指定：mysqldump -uxxx -p aazj --extended-insert=0 Users > Users.sql; =0 表示關閉選項。

上面這些預設選項，最好結合一個例子來理解：

-- MySQL dump 10.13  Distrib 5.6.26, for linux-glibc2.5 (i686)
--
-- Host: localhost    Database: gs
-- ------------------------------------------------------
-- Server version    5.6.26-log

/*!40101 SET @[email protected]@CHARACTER_SET_CLIENT */;
/*!40101 SET @[email protected]@CHARACTER_SET_RESULTS */;
/*!40101 SET @[email protected]@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40103 SET @[email protected]@TIME_ZONE */;
/*!40103 SET TIME_ZONE='+00:00' */;
/*!40014 SET @[email protected]@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @[email protected]@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @[email protected]@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @[email protected]@SQL_NOTES, SQL_NOTES=0 */;

--
-- Current Database: `gs`
--

CREATE DATABASE /*!32312 IF NOT EXISTS*/ `gs` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_bin */;

USE `gs`;

--
-- Table structure for table `user`
--

DROP TABLE IF EXISTS `user`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(30) COLLATE utf8mb4_bin DEFAULT NULL,
  `sex` tinyint(4) DEFAULT NULL,
  `phone` varchar(20) COLLATE utf8mb4_bin DEFAULT NULL,
  `addr` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `user`
--

LOCK TABLES `user` WRITE;
/*!40000 ALTER TABLE `user` DISABLE KEYS */;
INSERT INTO `user` VALUES (1,'yuanfang',1,'14465463786','hangzhou'),(2,'Andy',0,'14465463786','beijing'),(3,'peter',0,'14465463786','Hongkong');
/*!40000 ALTER TABLE `user` ENABLE KEYS */;
UNLOCK TABLES;
/*!40103 SET [email protected]_TIME_ZONE */;

/*!40101 SET [email protected]_SQL_MODE */;
/*!40014 SET [email protected]_FOREIGN_KEY_CHECKS */;
/*!40014 SET [email protected]_UNIQUE_CHECKS */;
/*!40101 SET [email protected]_CHARACTER_SET_CLIENT */;
/*!40101 SET [email protected]_CHARACTER_SET_RESULTS */;
/*!40101 SET [email protected]_COLLATION_CONNECTION */;
/*!40111 SET [email protected]_SQL_NOTES */;

-- Dump completed on 2015-10-22 10:16:37

mysqldump

2. mysqldump 登入伺服器的相關選項

Default options are read from the following files in the given order:

/etc/my.cnf /etc/mysql/my.cnf /usr/local/mysql/etc/my.cnf ~/.my.cnf


The following groups are read: mysqldump client
The following options may be given as the first argument:
--no-defaults           Don't read default options from any option file, except for login file.
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=# Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.

1）mysqldump 作為一個客戶端工具，它會去上訴目錄中尋找 my.cnf 檔案，然後讀取該檔案中 [mysqldump] 和 [client] 下面的選項；

2）那些 defaults 相關的選項都是為了另外指定 配置檔案和登入檔案，極少使用；

  -u, --user=name     User for login if not current user.

  -p, --password[=name] Password to use when connecting to server. If password is not given it's solicited on the tty.

  -h, --host=name     Connect to host.

  -P, --port=#        Port number to use for connection.
  --protocol=name     The protocol to use for connection (tcp, socket, pipe, memory).

  --max-allowed-packet=#  The maximum packet length to send to or receive from server.
  --net-buffer-length=#      The buffer size for TCP/IP and socket communication.

3）這幾個選項指定 登入的使用者名稱，密碼，mysqld IP地址，埠，連線使用的協議等等。

    一般常用的是 -h192.168.2.xx -uxxx -p ，如果mysqld預設埠不是3306，則需要使用 -Pxxx 指定埠.

    --max-allowed-packet 我們一般配置在my.cnf中。--net-buffer-length 是為了優化網路連線的socket buffer.

使用示例： mysqldump -h192.168.1.20 -uxxx -p -P3057

3. mysqldump 選擇備份內容的相關選項

我們可以選擇備份所有資料庫，某幾個資料庫，某一個數據庫，某一個數據庫中的某幾個表，某一個數據庫中的一個表；

可以選擇是否備份 儲存過程和函式，觸發器，排程事件.

1）選擇匯出的資料庫 和 表：

-A, --all-databases Dump all the databases. This will be same as --databases with all databases selected.

-B, --databases     Dump several databases. Note the difference in usage; in this case no tables are given. All name arguments are

                            regarded as database names. 'USE db_name;' will be included in the output.

database [tables]   匯出資料庫 database 中的表結構 和 表中資料；

2）選擇是否匯出 建庫，建表語句，是否匯出 表中的資料：

-n, --no-create-db  Suppress the CREATE DATABASE ... IF NOT EXISTS statement that normally is output for each dumped database if 

                             --all-databases or --databases is given. (不匯出建庫語句: CREATE DATABASE，也就是不導庫結構)

-t, --no-create-info Don't write table creation info. (不匯出建表語句)

-d, --no-data         No row information. (不匯出資料，有時我們僅僅需要匯出表結構，也就是建表語句就行了)

3）選擇是否匯出 儲存過程和函式，觸發器，排程事件：

-R, --routines      Dump stored routines (functions and procedures). (匯出儲存過程和函式)

--triggers            Dump triggers for each dumped table. (Defaults to on; use --skip-triggers to disable.) (匯出觸發器)

--skip-triggers     不匯出觸發器

-E, --events        Dump events. 匯出排程事件(根據備份的目的進行選擇，如果是搭建slave，那麼就不要匯出events.)

4）指定不匯出 某個庫的某個表：

--ignore-table=name   Do not dump the specified table. To specify more than one table to ignore, use the directive multiple times,

                                 once for each table.  Each table must be specified with both database and table names,

                                 e.g.,  --ignore-table=database.table. (在匯出資料庫時，排除某個或者某幾個表不匯出)

5) 按照 where 條件匯出：

  

 -w, --where='where_condition' Dump only selected records. Quotes are mandatory.

6）使用示例：

Dumping structure and contents of MySQL databases and tables.
Usage: mysqldump [OPTIONS] database [tables]
OR       mysqldump [OPTIONS] --databases [OPTIONS] DB1 [DB2 DB3...]
OR       mysqldump [OPTIONS] --all-databases [OPTIONS]

1> 匯出單表的結構和資料：mysqldump -uxxx -p db1 tb1 > tb1.sql; 匯出資料庫 db1 中的 表 tb1 的表結構 和 表中資料；

2> 匯出多表的結構和資料：mysqldump -uxxx -p db1 tb1 tb2 > tb1_tb2.sql; 匯出資料庫 db1 中的 表 tb1、tb2 的表結構 和 表中資料；

3> 匯出單表的結構：mysqldump -uxxx -p --no-data db1 tb1 > tb1.sql; 匯出資料庫 db1 中的 表 tb1 的表結構; 其實也可以使用: show create table tb1

4> 我們無法使用 mysqldump 到達 只匯出某個或某幾個表的資料，而不匯出建表語句的目的。

     但是我們可以使用 select * from table into outfile 'file.sql', 比如：select * from Users into outfile '/tmp/Users.sql'; 注意需要對目錄的寫許可權。

5> 匯出單個庫中庫結構、表結構、表資料：mysqldump -uxxx -p --databases db1 > db1.sql

6> 匯出多個庫中庫結構、表結構、表資料：mysqldump -uxxx -p --databases db1 db2 > db1_db2.sql

7> 匯出單個庫中庫結構、表結構、不要表資料：mysqldump -uxxx -p --no-data --databases db1 > db1.sql

8> 匯出單個庫中資料，不要庫結構和表結構：mysqldump -uxxx -p --no-create-db --no-create-info --databases db1 > db1.sql

9> 匯出多個庫中庫結構、表結構、不要表資料：mysqldump -uxxx -p --no-data --databases db1 db2 > db1_db2.sql

10> 匯出資料庫中所有 庫 的庫結構，表結構，資料：mysqldump -uxxx -p --all-databases > all.sql

11> 匯出資料庫中所有 庫 的庫結構，表結構，不要資料：mysqldump -uxxx -p --all-databases --no-data > all.sql

12> 匯出單個庫中庫結構、表結構、表資料，排除某個表：mysqldump -uxxx -p --databases db1 --ignore-table=db1.test > db1.sql

4. mysqldump 事務 和 資料一致性(鎖) 的相關選項

在使用mysqldump邏輯備份時，事務和資料一致性的選項時至關重要的。

1） --single-transaction 

      Creates a consistent snapshot by dumping all tables in a single transaction. Works ONLY for tables stored in storage engines which

      support multiversioning (currently only InnoDB does); the dump is NOT guaranteed to be consistent for other storage engines.

      While a --single-transaction dump is in process, to ensure a valid dump file (correct table contents and binary log position), no other

      connection should use the following statements: ALTER TABLE, DROP TABLE, RENAME TABLE, TRUNCATE TABLE, as consistent

      snapshot is not isolated from them. Option automatically turns off --lock-tables.

     --single-transaction 可以得到一致性的匯出結果。他是通過將匯出行為放入一個事務中達到目的的。

     它有一些要求：只能是 innodb 引擎；匯出的過程中，不能有任何人執行 alter table, drop table, rename table, truncate table等DDL語句。

     實際上DDL會被事務所阻塞，因為事務持有表的metadata lock 的共享鎖，而DDL會申請metadata lock的互斥鎖，所以阻塞了。

     --single-transaction 會自動關閉 --lock-tables 選項；上面我們說到mysqldump預設會打開了--lock-tables，它會在匯出過程中鎖定所有表。

    因為 --single-transaction 會自動關閉--lock-tables，所以單獨使用--single-transaction是不會使用鎖的。與 --master-data 合用才有鎖。

2）--lock-tables

     該選項預設開啟的，上面已經說到了。它的作用是在匯出過程中鎖定所有表。--single-transaction 和 --lock-all-tables 都會將該選項關閉。

3）--lock-all-tables 
       Locks all tables across all databases. This is achieved by taking a global read lock for the duration of the whole dump.
       Automatically turns --single-transaction and --lock-tables off. 啟用該選項，會自動關閉 --single-transaction 和 --lock-tables.

上面三個選項中，只有 --lock-tables 預設是開啟的；開啟 --single-transaction 或者 開啟 --lock-all-tables 都將關閉 --lock-tables. 而--lock-all-tables會自動關閉 --single-transaction 和 --lock-tables。所以三者是互斥的。我們應該一次只啟用其中一個選項。

4）--flush-logs   

        Flush logs file in server before starting dump. Note that if you dump many databases at once (using the option --databases= or

        --all-databases), the logs will be flushed for each database dumped. The exception is when using --lock-all-tables or

        --master-data: in this case the logs will be flushed only once, corresponding to the moment all tables are locked. So if you want your

       dump and the log flush to happen at the same exact moment you should use --lock-all-tables or --master-data with --flush-logs.

       為了獲得匯出資料和重新整理日誌的一致性(同時發生)，必須將 --flush-logs 選項和 --lock-all-tables 或者 --master-data 一起使用：

       mysqldump --flush-logs --lock-all-tables;  mysqldump --flush-logs --master-data=2 ；

5）--flush-privileges 

      Emit a FLUSH PRIVILEGES statement 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 restore.

      如何匯出包含了mysql資料，就應該啟用該選項。該選項會在匯出的 mysql 資料庫的後面加上 flush privileges 語句，因為在向mysql資料庫inert了語句

      之後，必須使用 flush privileges，不然許可權不生效。下面是例子：

6）  --master-data[=#]  

       This causes the binary log position and filename to be appended to the output. If equal to 1, will print it as a CHANGE MASTER

       command; if equal to 2, that command will be prefixed with a comment symbol. This option will turn --lock-all-tables on, unless

       --single-transaction is specified too (in which case a global read lock is only taken a short time at the beginning of the dump; don't
       forget to read about --single-transaction below). In all cases, any action on logs will happen at the exact moment of the dump.

       Option automatically turns --lock-tables off.

所以為了獲得一致性的備份資料和在備份是同時重新整理binary日誌，我們應該如下結合使用這些選項(完美組合)：

mysqldump -uxxx -pxxx --single-transaction --master-data=2 --flush-logs --routines --databases db1 > db1.sql;

(其中 --flush-logs 不是必須的; 搭建slave時，不要匯出events，但是需要匯出rountines.)

其中被 --master-data 開啟的 --lock-all-tables 選項，又被 --single-transaction 關閉掉了。--flush-logs 藉助於 --master-data 可以達到即使一次匯出多個數據庫時，其 flush 的二進位制日誌也是在同一個時間點的，不是每一個數據庫flush一次的。並且這個時間點 和 --master-data 記錄的 binary log position 和 binary log file是同一個時間點，這些都是利用了 --single-transaction 和 --master-data 合用時短暫的使用一個全域性的讀鎖來達到目的的。

5. mysqldump 複製 的相關選項

1）  --master-data[=#]  

       This causes the binary log position and filename to be appended to the output. If equal to 1, will print it as a CHANGE MASTER

       command; if equal to 2, that command will be prefixed with a comment symbol. This option will turn --lock-all-tables on, unless

       --single-transaction is specified too (in which case a global read lock is only taken a short time at the beginning of the dump;

       don't forget to read about --single-transaction below). In all cases, any action on logs will happen at the exact moment of the dump.

       Option automatically turns --lock-tables off.

       該選項，上面已經介紹了。--master-data=1 表示會匯出 change master to 語句，--master-data=2 該語句放在註釋中，預設是為 0 。

       一般會和 --single-transaction一起使用，用於搭建master-slave環境。

下面是 --master-data=1 和 --master-data=2 的比較：

 

在匯出檔案的前30行左右可以看到 change master to 語句。可以使用 head -n 30 db1.sql 檢視

2）  --dump-slave[=#]   

      This causes the binary log position and filename of the master to be appended to the dumped data output. Setting the value to 1, will

      printit as a CHANGE MASTER command in the dumped data output; if equal to 2, that command will be prefixed with a comment

      symbol. This option will turn --lock-all-tables on, unless --single-transaction is specified too (in which case a global read lock is only

      taken a short time at the beginning of the dump - don't forget to read about --single-transaction below). In all cases any action on

      logs will happen at the exact moment of the dump.Option automatically turns --lock-tables off.

      --dump-slave 和 --master-data 幾乎一樣。區別只是--dump-slave用於slave建立下一級的slave；而 --master-data用於master建立slave;

      如果在 master 上使用 --dump-slave 會報錯：mysqldump: Couldn't execute 'START SLAVE': The server is not configured as slave;

3） --apply-slave-statements 
       Adds 'STOP SLAVE' prior to 'CHANGE MASTER' and 'START SLAVE' to bottom of dump.

       在 change master 匯出 stop slave 語句, 在 change master 之後匯出 start slave語句。其實是一個自動化的處理。和 --master-data=1 類似。

如下圖所示：開頭有 stop slave, 結尾有 start slave語句：

4）--include-master-host-port 
      Adds 'MASTER_HOST=<host>, MASTER_PORT=<port>' to 'CHANGE MASTER TO..' in dump produced with --dump-slave.

      該選擇要結合 --dump-slave=1/2 使用。會在匯出中加入 host。

5）--include-master-host-port 
     Adds 'MASTER_HOST=<host>, MASTER_PORT=<port>' to 'CHANGE MASTER TO..' in dump produced with --dump-slave.

     該選擇要結合 --dump-slave=1/2 使用。會在匯出中加入mysql的 port。

6）--delete-master-logs 
     Delete logs on master after backup. This automatically enables --master-data.

     在備份之後，刪除 master上的binary log。該選項會自動開啟 --master-data 選項(等於2)。該選項一般不用。日誌一般不能隨便刪除。

7）--set-gtid-purged[=name] 
     Add 'SET @@GLOBAL.GTID_PURGED' to the output. Possible values for this option are ON, OFF and AUTO. If ON is used and GTIDs

     are not enabled on the server, an error is generated. If OFF is used, this option does nothing. If AUTO is used and GTIDs are enabled

     on the server, 'SET @@GLOBAL.GTID_PURGED' is added to the output. If GTIDs are disabled, AUTO does nothing. If no value is

     supplied then the default (AUTO) value will be considered.

     該選項用於啟用了GTID特性的環境。

6. mysqldump 字符集 的相關選項

1）--set-charset      

     Add 'SET NAMES default_character_set' to the output.  (Defaults to on; use --skip-set-charset to disable.)

    --set-charset=1/0 開啟和關閉。也可以使用 --skip-set-charset 關閉。

   該選項我們上面已經說到了。表示是否生成 /*!40101 SET NAMES utf8 */;

2）-N, --no-set-names 

     Same as --skip-set-charset. 關閉 --set-charset. 不生成 /*!40101 SET NAMES utf8 */; 語句。

3）--default-character-set=name 
     Set the default character set.

     該選項上面也涉及到了。指定語句：/*!40101 SET NAMES utf8 */;中的字符集；可能你需要改成 --default-character-set=utf8mb4

7. mysqldump 控制是否生成 DDL 語句 的相關選項

  --add-drop-database  Add a DROP DATABASE before each create.
  --add-drop-table        Add a DROP TABLE before each create.  (Defaults to on; use --skip-add-drop-table to disable.)
  --add-drop-trigger      Add a DROP TRIGGER before each create.

  --no-create-db,-n 

  --no-create-info,-t

8. mysqldump 匯出格式 的相關選項

1）--compatible=name  

     Change the dump to be compatible with a given mode. By default tables are dumped in a format optimized for MySQL.

     Legal modes are: ansi, mysql323, mysql40, postgresql, oracle, mssql, db2, maxdb, no_key_options, no_table_options,

     no_field_options. One can use several modes separated by commas. Note: Requires MySQL server version 4.1.0 or higher.

     This option is ignored with earlier server versions.

     匯出sql語句的相容格式。如果我們需要從MySQL匯出，然後匯入到其它資料庫，則可使用該選項。--compatible=oracle/postgresql/mssql

2）-Q, --quote-names  

     Quote table and column names with backticks (`). (Defaults to on; use --skip-quote-names to disable.)

     將表名和列名使用 ``包裹。以防他們是關鍵字時報錯。

9. mysqldump 錯誤處理的相關選項

1）-f, --force              Continue even if we get an SQL error.

2）--log-error=name    Append warnings and errors to given file.

10. mysqldump 實現原理

為了探求 mysqldump 的備份是如何實現的，我們需要在 my.cnf 中的[mysqld] 引數段加入：

general_log=on
general_log_file=general.log

 這樣我們就可以通過觀察 general.log 的輸出，來了解 mysqldump 的備份是如何實現的。

1）--lock-tables 是如何實現的：

先執行：mysqldump -uroot -p --databases gs --lock-tables > gs_l.sql， 然後檢視 general.log:

Init DB   gs
Query     SHOW CREATE DATABASE IF NOT EXISTS `gs`
Query     show tables
Query     LOCK TABLES `tb1` READ /*!32311 LOCAL */,`user` READ /*!32311 LOCAL */
Query     show table status like 'tb1'
Query     SET SQL_QUOTE_SHOW_CREATE=1
Query     SET SESSION character_set_results = 'binary'
Query     show create table `tb1`
Query     SET SESSION character_set_results = 'utf8'
Query     show fields from `tb1`
Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `tb1`
Query     SET SESSION character_set_results = 'binary'
Query     use `gs`
Query     select @@collation_database
Query     SHOW TRIGGERS LIKE 'tb1'
Query     SET SESSION character_set_results = 'utf8'
Query     show table status like 'user'
Query     SET SQL_QUOTE_SHOW_CREATE=1
Query     SET SESSION character_set_results = 'binary'
Query     show create table `user`
Query     SET SESSION character_set_results = 'utf8'
Query     show fields from `user`
Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `user`
Query     SET SESSION character_set_results = 'binary'
Query     use `gs`
Query     select @@collation_database
Query     SHOW TRIGGERS LIKE 'user'
Query     SET SESSION character_set_results = 'utf8'
Query     UNLOCK TABLES
Quit

 

1> 第一步： SHOW CREATE DATABASE IF NOT EXISTS `gs`; 匯出了建庫語句；

2> 第二步：show tables; 獲得資料庫中所有表名，然後鎖住：LOCK TABLES `tb1` READ /*!32311 LOCAL */,`user` READ /*!32311 LOCAL */

                使用的是 lock table tb1 read local, tb2 read local, tb3 read local; 語句

3> 第三步：show create table 'tb1'; 匯出了 tb1 的建表語句；

4> 第四步：show fields from `tb1`; SELECT /*!40001 SQL_NO_CACHE */ * FROM `tb1`; 匯出了表中的資料；

......

5> 最後匯出了 trigger, 最後的最後 unlock tables; 結束。

可以看到 --lock-tables 在匯出一個數據庫時，會在整個匯出過程 lock read local 所有的表。該鎖不會阻止其它session讀和插入。

2）--lock-all-tables 的實現：

先執行：mysqldump -uroot -p --databases gs --lock-all-tables > gs_l.sql， 在檢視 general.log:

14:34:13     4 Connect   [email protected] on
Query     /*!40100 SET @@SQL_MODE='' */
Query     /*!40103 SET TIME_ZONE='+00:00' */
Query     FLUSH TABLES
Query     FLUSH TABLES WITH READ LOCK
Query     SHOW VARIABLES LIKE 'gtid\_mode'
                    ... ...
Init DB   gs
Query     SHOW CREATE DATABASE IF NOT EXISTS `gs`
Query     show tables
                    ... ...4 Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `tb1`
Query     SET SESSION character_set_results = 'binary'
Query     use `gs`
Query     select @@collation_database
                    ... ...
Query     show fields from `user`
Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `user`
Query     SET SESSION character_set_results = 'binary'
Query     use `gs`
Query     select @@collation_database
Query     SHOW TRIGGERS LIKE 'user'
Query     SET SESSION character_set_results = 'utf8'
Quit

它的實現使用了 FLUSH TABLES; FLUSH TABLES WITH READ LOCK; 語句。在最後沒有看到解鎖語句。

它請求發起一個全域性的讀鎖，會阻止對所有表的寫入操作，以此來確保資料的一致性。備份完成後，該會話斷開，會自動解鎖。

3）--single-transaction 的實現：

先執行： mysqldump -uroot -p --databases gs --single-transaction > gs_l.sql，在檢視 general.log:

14:41:34     5 Connect   [email protected] on
Query     /*!40100 SET @@SQL_MODE='' */
Query     /*!40103 SET TIME_ZONE='+00:00' */
Query     SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ
Query     START TRANSACTION /*!40100 WITH CONSISTENT SNAPSHOT */
Query     SHOW VARIABLES LIKE 'gtid\_mode'
Query     UNLOCK TABLES
                    ... ...
Init DB   gs
Query     SHOW CREATE DATABASE IF NOT EXISTS `gs`
Query     SAVEPOINT sp
                    ......
Query     show create table `tb1`
                    ......5 Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `tb1`
                   ......
Query     ROLLBACK TO SAVEPOINT sp
                   ......
Query     show create table `user`
                    .....5 Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `user`
                    ......
Query     ROLLBACK TO SAVEPOINT sp
Query     RELEASE SAVEPOINT sp
Quit

基本過程是：

1> 先改變事務隔離級別：SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ

2> 開始事務：START TRANSACTION /*!40100 WITH CONSISTENT SNAPSHOT */

3> unlock tables;

4> 匯出建庫語句； SHOW CREATE DATABASE IF NOT EXISTS `gs`

5> 開啟一個 savepoint: SAVEPOINT sp;

6> 匯出 表 tb1 的結構和資料；

7> ROLLBACK TO SAVEPOINT sp; 回滾到savepoint;

對其它表重複該過程；

8> 最後 realease savepoint p; 釋放savepoint;

整個過程，沒有任何鎖。RR隔離級別保證在事務中只讀取本事務之前的一致性的資料。 rollback to savepoint sp; 保證了對資料庫中的資料沒有影響。

4）--master-data 的實現：

先執行：mysqldump -uroot -p --databases gs --master-data=1 > gs_l.sql，在檢視general.log:

14:57:45     6 Connect   [email protected] on
Query     /*!40100 SET @@SQL_MODE='' */
Query     /*!40103 SET TIME_ZONE='+00:00' */
Query     FLUSH /*!40101 LOCAL */ TABLES
Query     FLUSH TABLES WITH READ LOCK
Query     SHOW VARIABLES LIKE 'gtid\_mode'
Query     SHOW MASTER STATUS

發現了 --lock-all-tables一樣，就多了一句：show master status;

5）--single-transaction 和 --master-data 結合使用：

先執行：mysqldump -uroot -p --databases gs --master-data=1 > gs_l.sql，在檢視general.log:

15:00:56     7 Connect   [email protected] on
Query     /*!40100 SET @@SQL_MODE='' */
Query     /*!40103 SET TIME_ZONE='+00:00' */
Query     FLUSH /*!40101 LOCAL */ TABLES
Query     FLUSH TABLES WITH READ LOCK
Query     SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ
Query     START TRANSACTION /*!40100 WITH CONSISTENT SNAPSHOT */
Query     SHOW VARIABLES LIKE 'gtid\_mode'
Query     SHOW MASTER STATUS
Query     UNLOCK TABLES
                    ......
Init DB   gs
Query     SHOW CREATE DATABASE IF NOT EXISTS `gs`
Query     SAVEPOINT sp
Query     show create table `tb1`
Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `tb1`
Query     ROLLBACK TO SAVEPOINT sp
Query     show create table `user`
Query     SELECT /*!40001 SQL_NO_CACHE */ * FROM `user`
Query     ROLLBACK TO SAVEPOINT sp
Query     RELEASE SAVEPOINT sp
Quit

發現 --single-transaction 單獨使用 與 --single-transaction 和 --master-data 結合使用 的區別如下圖：

--single-transaction 和 --master-data 結合使用時，在匯出開始，會短暫的持有一個全域性的讀鎖，鎖定時：重新整理資料到磁碟、設定隔離級別為RR、開始事務、輸出 binary log 的位置和檔名，然後解鎖。這樣就保證了：show master status 輸出的 binary log 的位置和檔名 和 後面 匯出的資料是同一個時間點的(同一個lsn)，所以才能使用該備份 和 利用 change master to 構造一個 slave，成功的連線上 master.

可以看到這裡使用了兩次 flush tables:

FLUSH /*! 40101 LOCAL */ TABLES

FLUSH TABLES WITH READ LOCK

其原因是 第一次 flush 是不需要鎖表的，第一次將所有資料重新整理到磁碟之後，第二次 FLUSH TABLES WITH READ LOCK 時就會只有很少量的資料需要重新整理到磁碟，所以第一次 flush 是為了儘量的 減少 第二次  fush 持有鎖的時間