Oracle数据库开发从C语言开始（c 引用oracle类）

Oracle数据库开发：从C语言开始

Oracle数据库是一个功能强大的关系型数据库管理系统，广泛应用于企业级应用程序和大型网站。数据库开发需要熟悉SQL语言和相关的编程语言。本文将讲解如何在C语言中连接Oracle数据库并进行基本的数据库操作。

1. 安装Oracle Instant Client

Oracle Instant Client是一种基于轻便式管理库的客户端软件，用于连接Oracle数据库。你可以访问Oracle官网下载对应的Instant Client，也可以通过以下命令在Ubuntu中安装：

sudo apt-get install alien
sudo alien oracle-instantclient12.1-basic-12.1.0.2.0-1.x86_64.rpm
sudo dpkg -i oracle-instantclient12.1-basic_12.1.0.2.0-2_amd64.deb

2. 配置环境变量并建立连接

在C语言中，需要包含oci.h头文件进行连接，同时需要设置相关的环境变量。以下是示例代码：

#include 
#include 
#include 
int mn(void) {
    OCIEnv *envhp;
    OCIError *errhp;
    OCIServer *srvhp;
    OCISession *authp;

    OCIDefine *defhp;
    OCIStmt *stmthp;
    OCIDescribe *dschp;
    OCIBind *bindhp;
    int status;

    OCIInitialize((ub4) OCI_DEFAULT, (dvoid *)0,
                  (dvoid * (*)(dvoid *, size_t)) 0,
                  (dvoid * (*)(dvoid *, dvoid *, size_t))0,
                  (void (*)(dvoid *, dvoid *)) 0 );
    OCIEnvInit( &envhp, OCI_DEFAULT, 0, (dvoid **)0);

    OCIHandleAlloc((dvoid *) envhp, (dvoid **) &errhp, OCI_HTYPE_ERROR, (size_t) 0, (dvoid **) 0);

    OCILogon(envhp, errhp, &srvhp, "username", strlen("username"),
             "password", strlen("password"), "dbname", strlen("dbname"));
    OCIHandleAlloc( (dvoid *) envhp, (dvoid **) &authp, OCI_HTYPE_SESSION, 0, (dvoid **) 0);
    OCIAttrSet((dvoid *)authp, OCI_HTYPE_SESSION, (dvoid *) &srvhp,
               (ub4) 0, OCI_ATTR_SERVER, (OCIError *) errhp);
    OCIAttrSet((dvoid *)authp, OCI_HTYPE_SESSION, (dvoid *) "username",
               (ub4) strlen("username"), OCI_ATTR_USERNAME, errhp);
    OCIAttrSet((dvoid *)authp, OCI_HTYPE_SESSION, (dvoid *) "password",
               (ub4) strlen("password"), OCI_ATTR_PASSWORD, errhp);

    status = OCISessionBegin ( srvhp, errhp, authp, OCI_CRED_RDBMS, OCI_DEFAULT );
    OCIHandleFree((dvoid *)authp, OCI_HTYPE_SESSION);
    OCIServerAttach ( srvhp, errhp, "dbname", strlen("dbname"), OCI_DEFAULT );

    // 此处省略对定义和初始化的过程

    OCIStmtPrepare(stmthp, errhp,
                   (CONST OraText*)"SELECT * FROM table_name WHERE column_name=:bind_value",
                   strlen("SELECT * FROM table_name WHERE column_name=:bind_value"),
                   OCI_NTV_SYNTAX, OCI_DEFAULT);
    OCIHandleAlloc((dvoid *)envhp, (dvoid **)&dschp, OCI_HTYPE_DESCRIBE, 0, (dvoid **)0);
    OCIDescribeAny(srvhp, errhp, (dvoid *)tablename, (ub4)strlen(tablename), OCI_OTYPE_NAME, (ub1)0, (ub1)OCI_PTYPE_TABLE, (OCIDescribe *)dschp);
    OCIAttrGet((CONST dvoid *)dschp, OCI_HTYPE_DESCRIBE, (dvoid *)&colcount, (ub4 *)sizeof(ub4), OCI_ATTR_PARAM_COUNT, (OCIError *)errhp);

    OCIHandleAlloc((dvoid *)envhp, (dvoid **)&bindhp, OCI_HTYPE_BIND, 0, (dvoid **)0);
    OCIBindByName(stmthp, &bindhp, errhp, (OraText *)":bind_value", strlen(":bind_value"),
                  (dvoid *)&bind_value, (sb4)sizeof(int), SQLT_INT, NULL, NULL, NULL, (ub4)0, NULL, OCI_DEFAULT);

    OCIStmtExecute(svchp, stmthp, errhp, 1, 0, NULL, NULL, OCI_DEFAULT);

    // 关闭连接
    OCISessionEnd(srvhp, errhp, authp, OCI_DEFAULT);
    OCIServerDetach(srvhp, errhp, OCI_DEFAULT);

    return 0;
}

3. 执行基本的数据库操作

通过OCIStmtPrepare函数，可以准备好一条SQL语句。在此基础上，可以使用OCIBind函数绑定变量，使用OCIStmtExecute函数执行SQL语句。以下是一个简单的例子，用于从table_name表中查询名字为name的记录：

OCIStmtPrepare(stmthp, errhp, (CONST OraText*)"SELECT * FROM table_name WHERE name=:bind_value",
               strlen("SELECT * FROM table_name WHERE name=:bind_value"),
               OCI_NTV_SYNTAX, OCI_DEFAULT);
OCIHandleAlloc((dvoid *)envhp, (dvoid **)&bindhp, OCI_HTYPE_BIND, 0, (dvoid **)0);
OCIBindByName(stmthp, &bindhp, errhp, (OraText *)":bind_value", strlen(":bind_value"),
              (dvoid *)&name, (sb4)strlen(name), SQLT_STR, NULL, NULL, NULL, (ub4)0, NULL, OCI_DEFAULT);
OCIStmtExecute(svchp, stmthp, errhp, 1, 0, NULL, NULL, OCI_DEFAULT);

除此之外，OCI还提供了很多其他的函数和操作，例如事务管理、游标操作等等。

本文介绍了如何在C语言中连接Oracle数据库，并执行基本的SQL操作。学习OCI可以帮助开发人员更好地了解Oracle数据库，为企业级应用程序和大型网站的数据库开发提供支持。