c++ and database errors

[gurupot]

In my c++ program I connect to the database and execute some SQL queries. Most of my statements execute fine but once in a while I get errors with my insert statements. I am printing out the error using the SQLError like this. unsigned char error[200], szSqlState[91];

  long  pfNativeError; 
    short pcbErrorMsg;
    ::SQLError(NULL,hdbc,hstmt,szSqlState,
      &pfNativeError,(unsigned char*)&error[0],199,&pcbErrorMsg);

    LogError("Error executing");
    LogError((char*)command);
    LogError((char*)error);
    ::SQLCancel(hstmt) ;

Most of the times when I get errors I get the error message in my log files stating an invalid column etc. But some times I get blank line for the error. Did anyone have the same problem. Why do I get a blank line. Please help.

[mlgoff]

Your post does not really contain adequate information to trouble shoot the problem. That said:

In my experience, when an error handler provides a blank message, most of the time it is because I am using an error handler that can trap the error but is the wrong one for providing error information. Below is a list of error handlers I have found/created over the years:

#include "Windows.h"
#include <stdexcept>

  try
  {
    diff_db_schema->PutRefActiveConnection(NULL);
  }
  catch(std::exception& e)
  {
    OutputDebugString(e.what());
  }
  catch( CNotSupportedException *e )
  {
    CString err_msg;  
    CRuntimeClass *pClass = e->GetRuntimeClass();

    err_msg = "MFC Exception ";
    err_msg += (LPCTSTR) pClass->m_lpszClassName;
    err_msg += " thrown\n";

    AfxMessageBox(err_msg, MB_ICONEXCLAMATION);
  }
  catch( CCommonDialog *e )
  {
    CString err_msg;  
    CRuntimeClass *pClass = e->GetRuntimeClass();

    err_msg = "MFC Exception ";
    err_msg += (LPCTSTR) pClass->m_lpszClassName;
    err_msg += " thrown\n";

    AfxMessageBox(err_msg, MB_ICONEXCLAMATION);
  }
  catch(_com_error &e)
  {
    CString err_msg;
    _variant_t error_num;

    error_num = e.Error();
    error_num.ChangeType(VT_BSTR);

    err_msg = "Error:\n";
    err_msg += "Code = ";
    err_msg += (CString)error_num.bstrVal;
    err_msg += "\n";
    err_msg += "Code meaning = ", (char*) e.ErrorMessage();
    err_msg += e.ErrorMessage();
    err_msg += "\n";
    err_msg += "Source = ";
    err_msg += (char*) e.Source();
    err_msg += "\n";
    err_msg += "Description = ";
    err_msg += (char*) e.Description();
    err_msg += "\n";

    AfxMessageBox(err_msg, MB_ICONEXCLAMATION);
    
    return false;
  }
  catch(CDaoException* e)
  {
    AfxMessageBox(e->m_pErrorInfo->m_strDescription, MB_ICONEXCLAMATION);
    e->Delete();
    return false;
  }
  catch(CFileException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch(CMemoryException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch(CArchiveException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch(CNotSupportedException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch(CResourceException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch(CDBException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch(COleException e)
  {

    TCHAR   szCause[255];
    CString strFormatted;

    e.GetErrorMessage(szCause, 255);
    strFormatted += szCause;
    AfxMessageBox(strFormatted);
    return false;
  } 
  catch( char *str )
  {
    AfxMessageBox(str, MB_ICONEXCLAMATION);
    return false;
  }
  catch( _variant_t var )
  {
    CString msg;

    var.ChangeType(VT_BSTR);
    msg = var.bstrVal;

    AfxMessageBox(msg, MB_ICONEXCLAMATION);
    return false;
  }
  catch( COleDispatchException *e )
  {
    CString err_msg;  

    err_msg.Format("MFC COleDispatchException #: %d \r\n"
                   "Description: %s "
                   "Source: %s ", 
                   e->m_wCode, 
                   e->m_strDescription, 
                   e->m_strSource);

    AfxMessageBox(err_msg, MB_ICONEXCLAMATION);

    success = false;
  }
  catch( CException *e )
  {
    CString err_msg;  
    CRuntimeClass *pClass = e->GetRuntimeClass();

    err_msg = "MFC Exception ";
    err_msg += (LPCTSTR) pClass->m_lpszClassName;
    err_msg += " thrown\n";

    AfxMessageBox(err_msg, MB_ICONEXCLAMATION);

    return false;
  }
  catch(...)
  {
      // requires Windows.h & stdlib.h
    DWORD dw = GetLastError(); 
    char szBuf[80];

    ltoa(dw, szBuf, 10); 

    LPVOID lpMsgBuf;
    FormatMessage( 
        FORMAT_MESSAGE_ALLOCATE_BUFFER | 
        FORMAT_MESSAGE_FROM_SYSTEM | 
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        GetLastError(),
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
        (LPTSTR) &lpMsgBuf,
        0,
        NULL);
    // Display the string.
    AfxMessageBox((LPCTSTR)lpMsgBuf, MB_OK | MB_ICONINFORMATION );
    // Free the buffer.
    LocalFree( lpMsgBuf );

    CloseHandle(file_handle);
    return false;
  }

One of these might give you a more meaningful message.