MySQL中dblink的实现

叁歲伎倆 2022-04-17 06:44 300阅读 0赞

参考 [https://blog.csdn.net/WYB213080286/article/details/38493753][https_blog.csdn.net_WYB213080286_article_details_38493753]

参照以下博客：[http://blog.csdn.net/renfengjun/article/details/18730977][http_blog.csdn.net_renfengjun_article_details_18730977]

最近项目中涉及MySQL数据库视图的创建，需要整合两个位于不同服务器上数据库的内容，就遇到了远程访问数据库的问题。在cracle中可以通过dblink来实现跨本地数据库来访问另外一个数据库中的数据。通过在网上查找，发现可以通过MySQL中的federated插件来实现类似的功能。

操作环境：

宿主机为win8系统，MySQL数据库，ip：192.168.1.98；从机为VMware虚拟机中的Linux系统，版本为CentOS6.5，MySQL数据库，ip：192.168.1.106。

实现功能：

可以在Linux系统中MySQL数据库（target端）中建立宿主机MySQL数据库（source端）中某个表的link，当在Linux中读取link表时，就相当于直接读取宿主机中的原始表内容。

实现步骤：

1.  查看target端（Linux虚拟机中）是否安装了federated插件：

mysql> show engines;

±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+  
| Engine | Support | Comment | Transactions | XA | Savepoints |  
±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+  
| CSV | YES | CSV storage engine | NO | NO | NO |  
| MRG\_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |  
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |  
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |  
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |  
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |  
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |  
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |  
| PERFORMANCE\_SCHEMA | YES | Performance Schema | NO | NO | NO |  
±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+

显示没有安装federated插件

1.  安装federated插件：

mysql>install plugin federated soname ‘ha\_federated.so’;

ERROR 1125 (HY000): Function ‘federated’ already exists

说明已经安装过了，但没有启用

\[root@localhost etc\]\# service mysql stop

\[root@localhost etc\]\# mysqld\_safe --federated &

\[root@localhost etc\]\# 140811 01:20:21 mysqld\_safe Logging to ‘/var/lib/mysql/localhost.localdomain.err’.  
140811 01:20:22 mysqld\_safe Starting mysqld daemon with databases from /var/lib/mysql

mysql> show engines;

±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+  
| Engine | Support | Comment | Transactions | XA | Savepoints |  
±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+  
| CSV | YES | CSV storage engine | NO | NO | NO |  
| MRG\_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |  
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |  
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |  
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |  
| FEDERATED |YES | Federated MySQL storage engine | NULL | NULL | NULL |  
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |  
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |  
| PERFORMANCE\_SCHEMA | YES | Performance Schema | NO | NO | NO |  
±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+

federated插件已经启用

1.  配置/etc/my.conf，设置federated为默认启动

\[root@localhost etc\]\# vi /etc/my.conf

在文件中加入一行：

federated

重启mysql服务

service mysql restart

mysql> show engines;

±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+  
| Engine | Support | Comment | Transactions | XA | Savepoints |  
±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+  
| CSV | YES | CSV storage engine | NO | NO | NO |  
| MRG\_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |  
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |  
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |  
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |  
| FEDERATED | YES | Federated MySQL storage engine | NULL | NULL | NULL |  
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |  
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |  
| PERFORMANCE\_SCHEMA | YES | Performance Schema | NO | NO | NO |  
±-------------------±--------±---------------------------------------------------------------±-------------±-----±-----------+

已经设置为默认启动了。

1.  在source端建立测试表，我是通过Navicat建立表的，其sql文件为：

DROP TABLE IF EXISTS `e_eledata`;  
CREATE TABLE `e_eledata` (  
`ID` bigint(20) unsigned NOT NULL auto\_increment COMMENT ‘ID’,  
`E_ELEMETERHEAD_ID` bigint(20) default NULL COMMENT ‘电表表头ID’,  
`DAQDT` timestamp NULL default NULL COMMENT ‘数据采集时间’,  
`DLDT` timestamp NULL default NULL COMMENT ‘数据入库时间’,  
`APCURRENT` decimal(10,3) default NULL COMMENT ‘A相电流。单位：A。’,  
`BPCURRENT` decimal(10,3) default NULL COMMENT ‘B相电流。单位：A。’,  
`CPCURRENT` decimal(10,3) default NULL COMMENT ‘C相电流。单位：A。’,  
`APVOLTAGE` decimal(10,3) default NULL COMMENT ‘A相电压。单位：V。’,  
`BPVOLTAGE` decimal(10,3) default NULL COMMENT ‘B相电压。单位：V。’,  
`CPVOLTAGE` decimal(10,3) default NULL COMMENT ‘C相电压。单位：V。’,  
PRIMARY KEY (`ID`)  
) ENGINE=MyISAM AUTO\_INCREMENT=1 DEFAULT CHARSET=utf8 COMMENT=‘电路数据表’;

1.  在target端建立link表，可以直接改写source表的sql脚本文件为：

DROP TABLE IF EXISTS `e_eledata_link`;  
CREATE TABLE `e_eledata_link` (  
`ID` bigint(20) unsigned NOT NULL auto\_increment COMMENT ‘ID’,  
`E_ELEMETERHEAD_ID` bigint(20) default NULL COMMENT ‘电表表头ID’,  
`DAQDT` timestamp NULL default NULL COMMENT ‘数据采集时间’,  
`DLDT` timestamp NULL default NULL COMMENT ‘数据入库时间’,  
`APCURRENT` decimal(10,3) default NULL COMMENT ‘A相电流。单位：A。’,  
`BPCURRENT` decimal(10,3) default NULL COMMENT ‘B相电流。单位：A。’,  
`CPCURRENT` decimal(10,3) default NULL COMMENT ‘C相电流。单位：A。’,  
`APVOLTAGE` decimal(10,3) default NULL COMMENT ‘A相电压。单位：V。’,  
`BPVOLTAGE` decimal(10,3) default NULL COMMENT ‘B相电压。单位：V。’,  
`CPVOLTAGE` decimal(10,3) default NULL COMMENT ‘C相电压。单位：V。’,  
PRIMARY KEY (`ID`)  
) ENGINE=FEDERATEDAUTO\_INCREMENT=1DEFAULT CHARSET=utf8 COMMENT=‘电路数据表’

CONNECTION='mysql://usrname:password@192.168.1.98:3306/databasename/table

其中：

usrname为宿主机中MySQL的用户名

password为相应的密码

（要保证该用户具有远程登陆的权限，可以通过以下命令来设置：

mysql>GRANT ALL PRIVILEGES ON *.* TO ‘usrname’@’%’ IDENTIFIED BY ‘password’ WITH GRANT OPTION;

其中\*.\*是指对用户开放所有数据库和表的权限，如果只开放某一个数据库的一个表为databasename.table；’%‘指的是该用户可以从任意的一个ip地址来远程访问数据库，包括本地，如果要限制用户从特定的ip来访问，将其改为’ip地址’）

192.168.1.98是source数据库的ip，这里为我宿主机的ip

3306为数据库的端口，默认一般为3306

database 和table分别为source端数据库的名称和表名称

将该sql脚本在target端运行

1.  实现跨本地数据库的访问

在target端通过访问e\_eledata\_link表来访问source端e\_eledata表

mysql> select \*from e\_eledata\_link;

[https_blog.csdn.net_WYB213080286_article_details_38493753]: https://blog.csdn.net/WYB213080286/article/details/38493753
[http_blog.csdn.net_renfengjun_article_details_18730977]: http://blog.csdn.net/renfengjun/article/details/18730977