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搭配使用 Visual FoxPro ODBC Driver 與 C 或 Visual C++ 應用程式

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C 或 C++ 應用程式會將 SQLExecute 或 SQLExecDirect 陳述式傳送至 Visual FoxPro，以與 Visual FoxPro 通訊。 此陳述式可以包含下列內容：

如需 Visual FoxPro 原生 SQL 的詳細資訊，請參閱 Visual FoxPro 文件。

範例：搭配使用 Visual FoxPro ODBC Driver 與 C 或 C++ 應用程式

下列範例會使用 ODBC C API 來擷取儲存在 Microsoft Visual FoxPro 範例資料庫之 Microsoft Visual FoxPro 範例資料庫中員工數據表中last_name字段中的數據。 此資料庫隨附 Visual FoxPro 提供，預設會安裝在下列位置：

c:\vfp\samples\mainsamp\data\tastrade.dbc

此範例會一次顯示一個姓氏，讓您按一下訊息方塊上的 [確定]，查看下一個姓氏。 此處預設已設定名為 Tastrade 的資料來源，用於使用 Tastrade.dbc 資料庫。

注意

您應該在所有 ODBC API 呼叫上執行錯誤檢查。為了簡潔起見，此範例會排除錯誤檢查的部分。

// FoxPro_ODBC_Driver_with_C.cpp  
// compile with: odbc32.lib user32.lib /c  
#include <windows.h>  
#include <sql.h>  
#include <sqlext.h>  
#include <stdio.h>  
#include <mbstring.h>  
  
#define MAX_DATA 100  
#define MYSQLSUCCESS(rc) ((rc==SQL_SUCCESS)||(rc==SQL_SUCCESS_WITH_INFO))  
  
class direxec {  
   RETCODE rc;        // ODBC return code  
   HENV henv;         // Environment     
   HDBC hdbc;         // Connection handle  
   HSTMT hstmt;       // Statement handle  
   unsigned char szData[MAX_DATA];   // Returned data storage  
   SDWORD cbData;     // Output length of data  
   unsigned char chr_ds_name[SQL_MAX_DSN_LENGTH];   // Data source name  
  
public:  
   direxec();           // Constructor  
   void sqlconn();      // Allocate env, stat, and conn  
   void sqlexec(unsigned char *);   // Execute SQL statement  
   void sqldisconn();   // Free pointers to env, stat, conn, and disconnect  
   void error_out();    // Displays errors  
};  
  
// Constructor initializes the string chr_ds_name with the data source name.  
direxec::direxec() {  
   _mbscpy_s(chr_ds_name, (const unsigned char *)"tastrade");  
}  
  
// Allocate environment handle, allocate connection handle,  
// connect to data source, and allocate statement handle.  
void direxec::sqlconn() {  
   SQLAllocEnv(&henv);  
   SQLAllocConnect(henv, &hdbc);  
   rc=SQLConnect(hdbc, chr_ds_name, SQL_NTS, NULL, 0, NULL, 0);  
  
   // Deallocate handles, display error message, and exit.  
   if (!MYSQLSUCCESS(rc)) {  
      SQLFreeEnv(henv);  
      SQLFreeConnect(hdbc);  
      error_out();  
      exit(-1);  
   }  
  
   rc = SQLAllocStmt(hdbc, &hstmt);  
}  
  
// Execute SQL command with SQLExecDirect() ODBC API.  
void direxec::sqlexec(unsigned char * cmdstr) {  
   rc = SQLExecDirect(hstmt, cmdstr, SQL_NTS);  
   if (!MYSQLSUCCESS(rc)) {   // Error  
      error_out();  
      // Deallocate handles and disconnect.  
      SQLFreeStmt(hstmt, SQL_DROP);  
      SQLDisconnect(hdbc);  
      SQLFreeConnect(hdbc);  
      SQLFreeEnv(henv);  
      exit(-1);  
   }  
   else {  
      for (rc = SQLFetch(hstmt) ; rc == SQL_SUCCESS; rc=SQLFetch(hstmt)) {  
         SQLGetData(hstmt, 1, SQL_C_CHAR, szData, sizeof(szData), &cbData);  
         // In this example, the data is returned in a messagebox for  
         // simplicity. However, normally the SQLBindCol() ODBC API could  
         // be called to bind individual data rows and assign for a rowset.  
         MessageBox(NULL, (const char *)szData, "ODBC", MB_OK);  
      }  
   }  
}  
  
// Free the statement handle, disconnect, free the connection handle, and  
// free the environment handle.  
void direxec::sqldisconn() {  
   SQLFreeStmt(hstmt, SQL_DROP);  
   SQLDisconnect(hdbc);  
   SQLFreeConnect(hdbc);  
   SQLFreeEnv(henv);  
}  
  
// Display error message in a message box that has an OK button.  
void direxec::error_out() {  
   unsigned char szSQLSTATE[10];  
   SDWORD nErr;  
   unsigned char msg[SQL_MAX_MESSAGE_LENGTH + 1];  
   SWORD cbmsg;  
  
   while(SQLError(0, 0, hstmt, szSQLSTATE, &nErr, msg, sizeof(msg), &cbmsg) == SQL_SUCCESS) {  
      sprintf_s((char *)szData, MAX_DATA, "Error:\nSQLSTATE=%s, Native error=%ld, msg='%s'",   
         szSQLSTATE, nErr, msg);  
  
      MessageBox(NULL, (const char *)szData, "ODBC Error", MB_OK);  
   }  
}  
  
int main (){  
   // Declare an instance of the direxec object.  
   direxec x;  
  
   // Allocate handles and connect.  
   x.sqlconn();  
  
   // Execute SQL command "SELECT last_name FROM employee".  
   x.sqlexec((UCHAR FAR *)"SELECT last_name FROM employee");  
  
   // Free handles, and disconnect.  
   x.sqldisconn();  
  
   // Return success code; example executed successfully.  
   return (TRUE);  
}