为什么pRecordset->Supports(adAddNew))总是返回FALSE？

TCHAR buf[256];
// swprintf(buf, _T("select DISTINCT * from dbo.TagView WHERE dbo.TagView.变量ID=%d"), pTag->m_nId);
swprintf(buf, _T("select DISTINCT * from dbo.变量基本信息 WHERE dbo.变量基本信息.变量ID=%d"), pTag->m_nId);

_RecordsetPtr pRecordset; // 记录集指针
HRESULT hr = pRecordset.CreateInstance(__uuidof(Recordset));
if (SUCCEEDED(hr))
{
hr = pRecordset->Open(
_variant_t(buf),
m_pConnect.GetInterfacePtr(),
adOpenStatic,
// adOpenDynamic,
// adLockOptimistic,
adLockBatchOptimistic,
adCmdText
);
if (SUCCEEDED(hr))
{
if(pRecordset->adoEOF)
{
if (pRecordset->Supports(adAddNew))
{
pRecordset->AddNew();
}
else
{
......