VC++ ADO方式访问数据库简要笔记

// VC++ ADO方式访问数据库
// By MoreWindows ( http://blog.csdn.net/MoreWindows )
#include <stdio.h>
#include <objbase.h>
//导入ADO库
#import "c:\program files\common files\system\ado\msado15.dll" no_namespace rename("EOF", "adoEOF")
int main()
{
	//初始化com环境
	CoInitialize(NULL);  
	_ConnectionPtr   pConnect(__uuidof(Connection));
	_RecordsetPtr    pRecord(__uuidof(Recordset));
	_CommandPtr      pCommand(__uuidof(Command));
	//__uuidof表示取和某个标示符相关联的GUID

	try
	{
		//连接Sql server数据库
		//数据库IP地址为222.197.165.36
		//数据库名为MyTestDB 用户名sa 密码4321
		pConnect->ConnectionString = "Provider=SQLOLEDB; Server=222.197.165.36; Database=MyTestDB; uid=sa; pwd=4321;";
		pConnect->Open("", "", "", adConnectUnspecified);
		
		//执行sql命令，结果记录在_RecordsetPtr中
		//数据表t_student中有id, name, age三列
		pCommand->put_ActiveConnection(_variant_t((IDispatch *)pConnect));
		pCommand->CommandText = "select id, name from t_student where age >= 18";
		pRecord = pCommand->Execute(NULL, NULL, adCmdText);

		_variant_t   vNum;
		_bstr_t      bstr;
		char         szName[100];

		while (!pRecord->adoEOF)
		{	
			// id
			vNum = pRecord->GetCollect("id");
			printf("%d     ", (int)vNum.intVal);
		
			// name
			vNum = pRecord->GetCollect("name"); //如果列名不对会引发错误
			bstr = vNum;        
			strcpy(szName, (PCSTR)bstr);
			printf("%s
", szName);

			// 取下一条记录
			pRecord->MoveNext();
		}
	}
	catch (_com_error err)
	{
		printf("Error! %s
", err.ErrorMessage());
	}
	
	pRecord->Close();
	pConnect->Close();
	pCommand.Release();
	pRecord.Release();
	pConnect.Release();

	//清空COM环境
	CoUninitialize();
	return 0;
}