1、导入库文件，并设置全局连接字符串

#import "C:\Program Files\Common Files\System\ado\msado60_Backcompat_i386.tlb" no_namespace rename("EOF","EndOfFile")

_ConnectionPtr pConn=NULL;	//数据库连接

2、在工程目录下新建SQL_connect.ini文件，并输入

Provider=MSDAORA.1;Password=test;User ID=test;Data Source=127.0.0.1:1521/orcl;Persist Security Info=True
127.0.0.1是指本机，如果连接到其他IP，直接修改该地址即可

连接数据库

if (!AfxOleInit())											//初始化OLE/COM库
	{
		AfxMessageBox(_T("OLE init Error"));
		return FALSE;
	}
	//创建数据库连接实例
	CStdioFile file; 
	file.Open(_T("SQL_Connect.ini"), CFile::modeRead);
	CString str=_T("");
	file.ReadString(str);
	file.Close();
	const _bstr_t strSRC = (_bstr_t)str;
	//const _bstr_t strSRC= "Provider=MSDAORA.1;Password=test;User ID=test;Data Source=localhost:1521/orcl;Persist Security Info=True";
	if (FAILED(pConn.CreateInstance("ADODB.Connection")))
	{
		AfxMessageBox(_T("Create Instance failed!"));
		exit(0);
	}
	try
	{
		pConn->Open(strSRC,"","",adModeUnknown);
	}
	catch(_com_error e)
	{
		AfxMessageBox(e.Description());
		exit(0);
	}

3、查询数据库

	<pre name="code" class="cpp">        CString str="R4-012345A010";
        CString coilnum;
	_variant_t  RecordsAffected;
	_RecordsetPtr pRecordset;
	//钢卷1
	str.Format(_T("select coilnum from test.test2 where coilnum like '%s'"), str);
	pRecordset = pConn->Execute((_bstr_t)str,&RecordsAffected,adCmdText);	//查询历史数据中当前卷信息
	if (!(pRecordset->BOF||pRecordset->EndOfFile) )	//存在历史数据
	{
		_variant_t var;
		var = pRecordset->GetFields()->GetItem((long)0)->GetValue();
		if(var.vt != VT_NULL)   //为NULL
		{m_coilnum = var;}
		else
		{m_coilnum = "";}
		
	}