c oracle实例

Oracle：世界顶级的数据库软件之一，广泛运用于企业级应用开发，尤其是业务资讯系统（OLTP）领域。C在Oracle中是用于操作Oracle数据库的低层语言。本文将介绍如何使用C语言调用Oracle实例。

在这个例子中，我们将使用C Orion API（Oracle内部API）来连接到Oracle数据库。首先需要确保安装了Oracle数据库和C开发环境。其中OCI（Oracle Call Interface）是用于在C语言中操作Oracle的最基本的API之一，其为C语言提供了访问Oracle数据库的接口。在接下来的例子中，我们将使用OCI的一些基本功能：

#include#include#include#includeint main()
{
OCIEnv *envhp;
OCIError *errhp;
OCIServer *srvhp;
OCISvcCtx *svchp;
OCISession *sesshp;
text *username = (text *)"username";
text *password = (text *)"password";
text *dbname = (text *)"dbname";
sword retval;
char errbuf[512];
retval = OCIEnvCreate(&envhp, OCI_DEFAULT, NULL, NULL, NULL, NULL, 0, NULL);
if (retval != OCI_SUCCESS)
{
printf("OCIEnvCreate failed with error %d", retval);
exit(1);
}
retval = OCIHandleAlloc((dvoid *)envhp, (dvoid **)&errhp, OCI_HTYPE_ERROR, 0, NULL);
if (retval != OCI_SUCCESS)
{
printf("OCIHandleAlloc failed with error %d", retval);
exit(1);
}
retval = OCIHandleAlloc((dvoid *)envhp, (dvoid **)&srvhp, OCI_HTYPE_SERVER, 0, NULL);
if (retval != OCI_SUCCESS)
{
printf("OCIHandleAlloc failed with error %d", retval);
exit(1);
}
retval = OCIHandleAlloc((dvoid *)envhp, (dvoid **)&svchp, OCI_HTYPE_SVCCTX, 0, NULL);
if (retval != OCI_SUCCESS)
{
printf("OCIHandleAlloc failed with error %d", retval);
exit(1);
}
retval = OCIServerAttach(srvhp, errhp, (text *)dbname, strlen((char *)dbname), OCI_DEFAULT);
if (retval != OCI_SUCCESS)
{
OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &retval, (text *)errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
printf("Failed to attach to server with error %s", errbuf);
exit(1);
}
retval = OCIAttrSet((dvoid *)svchp, OCI_HTYPE_SVCCTX, (dvoid *)srvhp, (ub4)0, OCI_ATTR_SERVER, errhp);
if (retval != OCI_SUCCESS)
{
OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &retval, (text *)errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
printf("Failed to set server attribute with error %s", errbuf);
exit(1);
}
retval = OCIHandleAlloc((dvoid *)envhp, (dvoid **)&sesshp, OCI_HTYPE_SESSION, 0, NULL);
if (retval != OCI_SUCCESS)
{
printf("OCIHandleAlloc failed with error %d", retval);
exit(1);
}
retval = OCIAttrSet((dvoid *)sesshp, OCI_HTYPE_SESSION, (dvoid *)username, (ub4)strlen((char *)username), OCI_ATTR_USERNAME, errhp);
if (retval != OCI_SUCCESS)
{
OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &retval, (text *)errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
printf("Failed to set username attribute with error %s", errbuf);
exit(1);
}
retval = OCIAttrSet((dvoid *)sesshp, OCI_HTYPE_SESSION, (dvoid *)password, (ub4)strlen((char *)password), OCI_ATTR_PASSWORD, errhp);
if (retval != OCI_SUCCESS)
{
OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &retval, (text *)errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
printf("Failed to set password attribute with error %s", errbuf);
exit(1);
}
retval = OCISessionBegin(svchp, errhp, sesshp, OCI_CRED_RDBMS, OCI_DEFAULT);
if (retval != OCI_SUCCESS)
{
OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &retval, (text *)errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
printf("Failed to begin session with error %s", errbuf);
exit(1);
}
retval = OCIAttrSet((dvoid *)svchp, OCI_HTYPE_SVCCTX, (dvoid *)sesshp, (ub4)0, OCI_ATTR_SESSION, errhp);
if (retval != OCI_SUCCESS)
{
OCIErrorGet((dvoid *)errhp, (ub4)1, (text *)NULL, &retval, (text *)errbuf, (ub4)sizeof(errbuf), OCI_HTYPE_ERROR);
printf("Failed to set session attribute with error %s", errbuf);
exit(1);
}
printf("Oracle session established successfully\n");
}

在上述代码中，我们首先创建一个OCI环境对象并为其分配错误处理对象、服务对象、服务上下文对象和会话对象，然后使用OCI连接API连接到Oracle服务器，并使用OCI属性API设置会话的用户名和密码，最后启动会话并将其绑定到服务上下文对象。如果顺利的话，将会在控制台上输出 "Oracle session established successfully"。

可以在此基础上进一步添加OCI操作API，来对Oracle实例执行增删改查等操作。

总结

在本文中，我们介绍了如何使用C语言来连接Oracle数据库。使用OCI提供了C语言程序员在Oracle中进行开发的便捷途径，它提供了一组完整的API，可以与Oracle进行交互，从而实现以下目标：

连接Oracle服务
管理会话对象
执行SQL语句
获取和更新数据

OCI提供了连接到Oracle实例、管理Oracle会话以及执行包括增删改查在内的操作的最基本工具。在这个基础上，我们可以进一步使用其他API和功能，来满足更为复杂的需求。