vc写数据库，Ado的_RecordsetPtr的requery函数的参数

Question

参数是什么？手头没有msdn帮助，thanks

Answer 1

void GetRowsX(void)
{
    HRESULT hr = S_OK;    // Define string variables.
    _bstr_t strCnn("Provider=sqloledb;Data Source=MyServer;"
            "Initial Catalog=pubs;User Id=sa;Password=;");    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _RecordsetPtr pRstEmployees = NULL;
    
    try 
    {
        // Open recordset with names and hire dates from employee table.
        TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));        pRstEmployees->Open("SELECT fName, lName, hire_date "
            "FROM Employee ORDER BY lName",strCnn, 
            adOpenStatic, adLockReadOnly,adCmdText);
         while (true) //continuous loop
        {
            int intLines = 0;            // Get user input for number of rows.
            printf("\nEnter number of rows to retrieve (0 to exit): ");
            int intRows;
            scanf("%d", &intRows);            if (intRows <= 0)
                break;            //Clear the screen for the next display
            system("cls");
            // If GetRowsOK is successful, print the results,
            // noting if the end of the file was reached.
            _variant_t avarRecords;            if (GetRowsOK(pRstEmployees, intRows, avarRecords))
            {
                long lUbound;
                HRESULT hr = SafeArrayGetUBound(avarRecords.parray, 
                    2,&lUbound);                if (hr == 0)
                {
                    if (intRows > lUbound + 1)
                    {
                        printf("\n(Not enough records in Recordset to "
                            "retrieve %d rows)\n", intRows);
                    }
                }
                printf("%d records found.", lUbound+1);                // Print the retrieved data.
                for (int intRecords = 0;intRecords < lUbound+1;
                     intRecords++)
                {
                    printf("\n ");                    long rgIndices[2];
                    rgIndices[0] = 0; 
                    rgIndices[1] = intRecords;
                    _variant_t result;
                    result.vt = VT_BSTR;                    hr= SafeArrayGetElement(avarRecords.parray, 
                        rgIndices, &result);                    if (hr == 0){printf("%s ",(LPCSTR)(_bstr_t)result);}                    rgIndices[0] = 1;                    hr= SafeArrayGetElement(avarRecords.parray, 
                        rgIndices, &result);                    if (hr == 0){printf("%s, ",(LPCSTR)(_bstr_t)result);}                    rgIndices[0] = 2;                    hr= SafeArrayGetElement(avarRecords.parray, 
                        rgIndices, &result);                    if (hr == 0){printf("%s",(LPCSTR)(_bstr_t)result);}                    intLines ++;                    if (intLines % 10 == 0)
                    {
                        printf("\nPress any key to continue...");
                        getch();                        intLines = 0;                        //Clear the screen for the next display
                        system("cls");
                    }
                }
            }
            else
            {
                // Assuming the GetRows error was due to data
                // changes by another user, use Requery to
                // refresh the Recordset and start over.
                printf("GetRows failed--retry?\n");
                char chKey;
                do
                {
                    chKey = getch();
                }while(toupper(chKey) != 'Y'  && toupper(chKey) != 'N');
                
                if(toupper(chKey) == 'Y')
                {
                    pRstEmployees->Requery(adOptionUnspecified);
                }
                else
                {
                    printf("GetRows failed!\n");
                    break;
                }
            }            // Because using GetRows leaves the current
            // record pointer at the last record accessed,
            // move the pointer back to the beginning of the
            // Recordset before looping back for another search.
            pRstEmployees->MoveFirst();
        }
        //Clean up objects before exit.
        pRstEmployees->Close();
    }  
    catch(_com_error &e)
    {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
        _variant_t vtConnect = pRstEmployees->GetActiveConnection();        // GetActiveConnection returns connect string if connection
        // is not open, else returns Connection object.
        switch(vtConnect.vt)
        {
            case VT_BSTR:
                PrintComError(e);
                break;
            case VT_DISPATCH:
                PrintProviderError(vtConnect);
                break;
            default:
                printf("Errors occured.");
                break;
        }
    }
}来源:msdn