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c如何连接oracle数据库

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行业动态
2025-02-03
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连接Oracle数据库的方法包括使用SQL*Plus、Oracle SQL Developer、JDBC等。SQL*Plus是命令行工具，适用于快速查询和数据库管理；Oracle SQL Developer是图形化工具，简化了连接和管理数据库的过程；JDBC则用于Java应用程序连接数据库。

在C语言中连接Oracle数据库是一个相对复杂的过程，需要使用Oracle提供的OCI（Oracle Call Interface）库，以下是详细的步骤和示例代码：

环境准备

1、安装Oracle客户端：确保你的系统上已经安装了Oracle Instant Client或完整版Oracle客户端。

2、设置环境变量：将Oracle客户端的库路径添加到系统的PATH环境变量中。

   export LD_LIBRARY_PATH=/path/to/oracle/instantclient:$LD_LIBRARY_PATH

3、包含头文件：在你的C程序中包含必要的头文件。

   #include <oci.h>

编写代码

以下是一个基本的示例程序，演示如何使用OCI连接到Oracle数据库并执行一个简单的查询。

初始化OCI环境

初始化OCI环境和错误处理结构。

OCIEnv *envhp;
OCIError *errhp;
if (OCIEnvCreate(&envhp, OCI_DEFAULT, 0, 0, NULL, NULL, 0, NULL) != OCI_SUCCESS) {
    fprintf(stderr, "Error initializing OCI environment
");
    return 1;
}
if (OCIEnvInit(envhp, 0, 0, 0) != OCI_SUCCESS) {
    fprintf(stderr, "Error initializing OCI environment
");
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}

分配句柄

为会话、服务器、服务上下文和错误处理分配句柄。

OCIServer *srvhp;
OCISession *usrhp;
OCIServiceContext *svchp;
if (OCIHandleAlloc(envhp, (dvoid **) &srvhp, OCI_HTYPE_SERVER, 0, 0) != OCI_SUCCESS) {
    fprintf(stderr, "Error allocating server handle
");
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}
if (OCIHandleAlloc(envhp, (dvoid **) &usrhp, OCI_HTYPE_SESSION, 0, 0) != OCI_SUCCESS) {
    fprintf(stderr, "Error allocating session handle
");
    OCIHandleFree((dvoid *) srvhp, OCI_HTYPE_SERVER);
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}
if (OCIHandleAlloc(envhp, (dvoid **) &svchp, OCI_HTYPE_SVCCTX, 0, 0) != OCI_SUCCESS) {
    fprintf(stderr, "Error allocating service context handle
");
    OCIHandleFree((dvoid *) usrhp, OCI_HTYPE_SESSION);
    OCIHandleFree((dvoid *) srvhp, OCI_HTYPE_SERVER);
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}

连接到数据库

使用OCILogon函数连接到数据库。

const char *db = "your_database";
const char *user = "your_username";
const char *pass = "your_password";
if (OCILogon(envhp, srvhp, errhp, user, strlen(user), pass, strlen(pass), db, strlen(db)) != OCI_SUCCESS) {
    fprintf(stderr, "Error logging on to the database
");
    OCIHandleFree((dvoid *) svchp, OCI_HTYPE_SVCCTX);
    OCIHandleFree((dvoid *) usrhp, OCI_HTYPE_SESSION);
    OCIHandleFree((dvoid *) srvhp, OCI_HTYPE_SERVER);
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}

执行SQL语句

准备并执行一个SQL查询。

const char *stmt = "SELECT * FROM your_table";
OCIStmt *stmthp;
if (OCIHandleAlloc(envhp, (dvoid **) &stmthp, OCI_HTYPE_STMT, 0, 0) != OCI_SUCCESS) {
    fprintf(stderr, "Error allocating statement handle
");
    OCILogoff(usrhp, errhp);
    OCIHandleFree((dvoid *) svchp, OCI_HTYPE_SVCCTX);
    OCIHandleFree((dvoid *) usrhp, OCI_HTYPE_SESSION);
    OCIHandleFree((dvoid *) srvhp, OCI_HTYPE_SERVER);
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}
if (OCIPrepare(stmthp, errhp, (const OraText *) stmt, strlen(stmt), OCI_NTV_SYNTAX, OCI_DEFAULT) != OCI_SUCCESS) {
    fprintf(stderr, "Error preparing statement
");
    OCIHandleFree((dvoid *) stmthp, OCI_HTYPE_STMT);
    OCILogoff(usrhp, errhp);
    OCIHandleFree((dvoid *) svchp, OCI_HTYPE_SVCCTX);
    OCIHandleFree((dvoid *) usrhp, OCI_HTYPE_SESSION);
    OCIHandleFree((dvoid *) srvhp, OCI_HTYPE_SERVER);
    OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);
    return 1;
}
// Execute the statement and fetch results (omitted for brevity)

清理资源

释放所有分配的资源。

OCIHandleFree((dvoid *) stmthp, OCI_HTYPE_STMT);
OCILogoff(usrhp, errhp);
OCIHandleFree((dvoid *) svchp, OCI_HTYPE_SVCCTX);
OCIHandleFree((dvoid *) usrhp, OCI_HTYPE_SESSION);
OCIHandleFree((dvoid *) srvhp, OCI_HTYPE_SERVER);
OCIHandleFree((dvoid *) envhp, OCI_HTYPE_ENV);