VC調(diào)用SQLServer存儲過程的通用方法，只需要普通的查詢就可以實(shí)現(xiàn)。
這里討論的是ADO調(diào)用存儲過程，按MSDN的例子，一般都是下面的調(diào)用方法（節(jié)選自MSDN）：
HRESULT hr = S_OK;
// Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstByRoyalty = NULL;
_RecordsetPtr pRstAuthors = NULL;
_CommandPtr pcmdByRoyalty = NULL;
_ParameterPtr pprmByRoyalty = NULL;
_ConnectionPtr pConnection = NULL;
_bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
"Initial Catalog=Pubs;User Id=sa;Password=;");
_bstr_t strMessage, strAuthorID;
int intRoyalty;
VARIANT vtRoyalty;
try
{
//Open a Connection.
TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
hr = pConnection->Open(strCnn,"","",NULL);
pConnection->CursorLocation = adUseClient;
//Open Command Object with one Parameter
TESTHR(pcmdByRoyalty.CreateInstance(__uuidof(Command)));
pcmdByRoyalty->CommandText = "byroyalty";
pcmdByRoyalty->CommandType = adCmdStoredProc;
//Define Integer/variant.
vtRoyalty.vt = VT_I2;
vtRoyalty.iVal = intRoyalty;
pprmByRoyalty = pcmdByRoyalty->CreateParameter(
"percentage",adInteger,adParamInput,sizeof(int),vtRoyalty);
pcmdByRoyalty->Parameters->Append(pprmByRoyalty);
pprmByRoyalty->Value = vtRoyalty;
//Create Recordset by executing the command
pcmdByRoyalty->ActiveConnection = pConnection;
pRstByRoyalty = pcmdByRoyalty->Execute(
NULL,NULL,adCmdStoredProc);
//執(zhí)行結(jié)果的處理，省略
pRstByRoyalty->Close();
pRstAuthors->Close();
pConnection->Close();
}
catch(_com_error &e)
{
//意外處理
}
}
必須指定執(zhí)行SQL語句的CommandType是adCmdStoredProc，存儲過程有參數(shù)就必須CreateParameter生成參數(shù)，這樣調(diào)用存儲過程就成了很麻煩的一件事情，必須針對不同的存儲過程生成不同的參數(shù)。一個(gè)兩個(gè)還可以接受，如果項(xiàng)目的業(yè)務(wù)邏輯比較復(fù)雜，需要依賴大量的存儲過程，并且項(xiàng)目的需求或功能可能要經(jīng)常變動(dòng)或擴(kuò)展，那就成了一個(gè)噩夢了。有沒有通用的方法呢？當(dāng)然有，只需要通用的查詢就可以實(shí)現(xiàn)。
_ConnectionPtr pConnection = NULL;
m_Conn.CreateInstance(__uuidof(Connection));
m_Conn->ConnectionString = "Provider=sqloledb;Data Source=srv;"Initial Catalog=Pubs;User Id=sa;Password=;";
m_Conn->Open("","","",NULL);
_variant_t m_param;
_bstr_t m_bstr;
int index = 0,nFieldCount;
_RecordsetPtr m_Rs;
m_Rs.CreateInstance(__uuidof(Recordset));
m_Rs->Open("select * from titles",(IDispatch*)(m_Conn->m_Conn),adOpenStatic, adLockReadOnly,adCmdText);
nFieldCount = m_Rs->Fields->Count;
while(!m_Rs->EndOfFile)
{
for(index=0;index < nFieldCount;index ++)
{
m_param.Clear();
m_param = (short)index;
m_param = m_Rs->Fields->GetItem(m_param);
if(m_param.vt != VT_NULL)
m_bstr = m_param;
else
m_bstr = "";
printf("%s\n",(char*)m_bstr);
}
m_Rs->MoveNext();
}
m_Rs->Close();
m_Conn->Close();
以上一段就是普通的執(zhí)行查詢SQL語句的代碼，簡單起見，去掉了所有防護(hù)和判斷代碼，對于MS SQLServer，如果是執(zhí)行返回結(jié)果集的存儲過程，比如Pubs的byroyalty，只需要把上面代碼中的"select * from titles"替換成"byroyalty 100"就可以了，即"過程名 參數(shù)1,參數(shù)2,..."形式。
這樣一來，不需要生成參數(shù)，只需要改變SQL語句，就實(shí)現(xiàn)了MS SQLServer存儲過程的調(diào)用，可以通用。但是對于返回參數(shù)的存儲過程，這段代碼就不行了，不過還是可以通過SQL語句解決：
“declare @q int exec checkpwd 'user','pwd',@ret = @q OUTPUT select @q”
checkpwd是一個(gè)存儲過程，兩個(gè)輸入?yún)?shù)，用戶名和密碼，第三個(gè)是輸出參數(shù)@ret，返回用戶驗(yàn)證的結(jié)果。通過執(zhí)行上面的SQL語句，把輸出參數(shù)作為結(jié)果集返回，就可以適應(yīng)上面的VC代碼了。返回值的存儲過程也是一樣，執(zhí)行“declare @q int,@return int exec @return = checkpwd 'user','pwd',@ret = @q OUTPUT select @q,@return”就可以了。