由于项目开发的需求，需要通过oracle访问mysql，必须配置“网关”,通过ODBC实现
总结了一下从oracle访问mysql的步骤：
1.先简单介绍下环境
操作系统：windows xp
oracle：10.0.2.0.1
mysql：5.0
2.下载mysql的odbc驱动，我用的是myodbc 3.5.1并安装
下载路径:http://dev.mysql.com/downloads/connector/odbc/3.51.html
3.配置odbc数据源，在控制面板中配置就可以了，使用系统DSN，取名为mysqltest
4.在E:\\oracle\\product\\10.2.0\\db_1\\hs\\admin下(E:\\oracle\\product\\10.2.0\\db_1为ORACLE_HOME的安装目录)建立initmysqltest.ora文件
输入：
HS_FDS_CONNECT_INFO = mysqltest
HS_FDS_TRACE_LEVEL = OFF
5.在E:\\oracle\\product\\10.2.0\\db_1\\network\\admin下修改
listener.ora
输入：
(SID_DESC =
(SID_NAME = mysql)
(ORACLE_HOME = E:\\oracle\\product\\10.2.0\\db_1)
(PROGRAM = hsodbc)
)
修改后的listener.ora如下:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = E:\\oracle\\product\\10.2.0\\db_1)
(PROGRAM = extproc)
)
(SID_DESC =
(SID_NAME = mysql)
(ORACLE_HOME = E:\\oracle\\product\\10.2.0\\db_1)
(PROGRAM = hsodbc)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
)
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = MAJY)(PORT = 1521))
)
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = MAJY)(PORT = 1541))
)
)
6.修改tnsnames.ora
输入：
mysqltest =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = MAJY)(PORT = 1541))
(CONNECT_DATA =
(SID=mysqltest)
)
(HS =ok)
)
7.创建dblink
create public database link mysqllink
connect to “ws” identified by “ws”
using ‘mysqltest’;
要注意用户名和密码处需要用双引号，否则Oracle所传输的都是大写字母，可能无法登录进入MySQL。
8.访问mysql库中的表user
select “username” from “user”@mysqllink
由于MySQL中的表名的大小写敏感，因此需要在进行SQL查询时对表名用双引号扩起来