C 语言驱动 Oracle 数据库（c 执行oracle）

C语言驱动Oracle数据库

Oracle是一种由Oracle公司开发的非常流行的关系型数据库管理系统，许多大型机构使用数据库来存储和管理数据。C语言是一种功能强大的编程语言，可以与许多软件系统进行交互，包括数据库。本文将介绍如何使用C语言来驱动Oracle数据库。

一、安装Oracle Instant Client

要与Oracle数据库进行交互，需要在计算机上安装Oracle Instant Client，它是一种轻量级版本的Oracle数据库客户端。通过以下步骤安装：

1.访问Oracle官网，下载Compatible Instant Client版本。

2.解压缩安装文件到任意文件夹，设置环境变量ORACLE_HOME和LD_LIBRARY_PATH。

3.下载和安装ODBC Driver和ODBC Driver Manager。

二、创建Oracle数据库连接

需要连接Oracle数据库，使用用户名和密码连接数据库，并为连接设置其他参数。要创建连接，请使用下列函数：

“`C

int OCILogon2(OCISvcCtx **svchp, OCIEnv* envhp, OCIError* errhp, CONST OraText *usern, ub4 usernl, CONST OraText *passw, ub4 passwl, CONST OraText *dbname, ub4 dbnamel, CONST OraText *tag, ub4 tagl, CONST OraText *attribs, ub4 num_attribs, OCIAuthInfo *authhp, ub4 mode);

其中svchp表示服务句柄，envhp表示环境句柄，errhp表示错误句柄，usern表示连接用户名，usernl表示连接用户名长度，passw表示连接密码，passwl表示连接密码长度，dbname表示数据库名称，dbnamel表示数据库名称长度，tag表示标签，tagl表示标签长度，attribs表示属性，num_attribs表示属性数量，authhp表示认证信息，mode表示模式。成功创建连接后，将返回0。

下列代码以UTF-8编码演示了如何创建Oracle数据库连接：

```C
#include 
#include 
#include   
#include  
#include  
int mn()
{
  setlocale(LC_CTYPE, "");
  OCIEnv *envhp;  
  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, (size_t) 0, (dvoid **) 0); 
  OCISvcCtx *svchp;  
  OCIError *errhp; 
  OCIHandleAlloc((dvoid *)envhp, (dvoid **)&svchp, OCI_HTYPE_SVCCTX, 0, (dvoid **)0);  
  OCIHandleAlloc((dvoid *)envhp, (dvoid **)&errhp, OCI_HTYPE_ERROR, 0, (dvoid **)0);  
  OCILogon2(envhp, errhp, &svchp, (OraText *)"username",(ub4)strlen("username"),  (OraText *)"password",(ub4)strlen("password"),  (OraText *)"hostname",(ub4)strlen("hostname"),  (OraText *)0,0, OCI_DEFAULT); 
  printf("Connected!\n");
  OCILogoff(svchp, errhp);  
  OCIHandleFree((dvoid *)svchp, OCI_HTYPE_SVCCTX);  
  OCIHandleFree((dvoid *)errhp, OCI_HTYPE_ERROR);
  OCITerminate((ub4) OCI_DEFAULT, (dvoid *)0,  
                   (dvoid * (*)(dvoid *, size_t)) 0,  
                   (dvoid * (*)(dvoid *, dvoid *, size_t)) 0,  
                   (void (*)(dvoid *, dvoid *)) 0 );
  return 0;
}

三、执行SQL查询

连接到Oracle数据库后，可以执行SQL查询，以检索数据或修改数据。要在C程序中执行一个SQL查询语句，可以使用以下函数：

“`C

int OCIStmtPrepare2(OCISvcCtx *svchp, OCIStmt **stmtp, OCIError *errhp, CONST OraText *stmttext, ub4 stmtt, CONST OraText *key, ub4 keyt, ub4 language, ub4 mode);

其中svchp代表服务句柄，stmtp表示语句句柄，errhp代表错误句柄，stmttext表示语句文本，stmtt表示语句长度，key表示关键词，keyt表示关键词长度，language表示语言类型，mode表示执行模式。执行成功后，将返回0。

下例演示如何执行SQL查询：

```C
#include 
#include 
#include   
#include  
#include  
int mn()
{
  setlocale(LC_CTYPE, "");
  OCIEnv *envhp;  
  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, (size_t) 0, (dvoid **) 0); 
  OCISvcCtx *svchp;  
  OCIError *errhp; 
  OCIHandleAlloc((dvoid *)envhp, (dvoid **)&svchp, OCI_HTYPE_SVCCTX, 0, (dvoid **)0);  
  OCIHandleAlloc((dvoid *)envhp, (dvoid **)&errhp, OCI_HTYPE_ERROR, 0, (dvoid **)0);  
  OCILogon2(envhp, errhp, &svchp, (OraText *)"username",(ub4)strlen("username"),  (OraText *)"password",(ub4)strlen("password"),  (OraText *)"hostname",(ub4)strlen("hostname"),  (OraText *)0,0, OCI_DEFAULT); 
  
  OCIStmt *stmtp;  
  char buffer[1024] = "SELECT * FROM CUSTOMERS";
  OCIStmtPrepare2(svchp, &stmtp, errhp, (OraText*)buffer, (ub4)strlen(buffer), (OraText*)NULL, 0, OCI_NTV_SYNTAX, OCI_DEFAULT);
  OCIStmtExecute(svchp, stmtp, errhp, 0, 0, NULL, NULL, OCI_DEFAULT);
  OCIRowid *row_id;  
  char name[50]; 
  OCIDefine *defnp1 = NULL, *defnp2 = NULL;
  OCIDefine *defnp3 = NULL, *defnp4 = NULL, *defnp5 = NULL, *defnp6 = NULL;
  int id, age;
  double salary;
  int intemp, ret;  
  for (int i = 1; ; i++) {  
      ret = OCIStmtFetch2(stmtp, errhp, 1, OCI_DEFAULT, 0, OCI_DEFAULT);  
      if (ret == OCI_NO_DATA) break;  
      OCIAttrGet(stmtp, OCI_HTYPE_STMT,  (void *)&row_id, 0, OCI_ATTR_ROWID, errhp);  
      OCIAttrGet(stmtp, OCI_HTYPE_STMT, (void *)&defnp1, i, OCI_ATTR_DESCRIBE_POSITION, errhp);  
      OCIAttrGet(defnp1, OCI_DTYPE_PARAM, (void *)&name, 0, OCI_ATTR_NAME,  errhp);  
      OCIAttrGet(stmtp, OCI_HTYPE_STMT, (void *)&defnp2, i, OCI_ATTR_DESCRIBE_POSITION, errhp);  
      OCIAttrGet(defnp2, OCI_DTYPE_PARAM, (void *)&id, 0, OCI_ATTR_DATA_TYPE, errhp); 
      OCIAttrGet(stmtp, OCI_HTYPE_STMT, (void *)&defnp3, i, OCI_ATTR_DESCRIBE_POSITION, errhp);  
      OCIAttrGet(defnp3, OCI_DTYPE_PARAM, (void *)&age, 0, OCI_ATTR_DATA_TYPE, errhp); 
      OCIAttrGet(stmtp, OCI_HTYPE_STMT, (void *)&defnp4, i, OCI_ATTR_DESCRIBE_POSITION, errhp);  
      OCIAttrGet(defnp4, OCI_DTYPE_PARAM, (void *)&salary, 0, OCI_ATTR_DATA_TYPE, errhp);
      printf("%s  %d  %d  %f\n", name, id, age, salary);  
  } 
  OCIStmtRelease(stmtp, errhp, NULL, 0, OCI_DEFAULT);
  
  OCILogoff(svchp, errhp);  
  OCIHandleFree((dvoid *)svchp, OCI_HTYPE_SVCCTX);  
  OCIHandleFree((dvoid *)errhp, OCI_HTYPE_ERROR);
  OCITerminate((ub