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How to catch ODBC failure ?

Posted on 1998-10-22
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Last Modified: 2013-11-20
I am using an ODBC connection to an SQL Server Database in my MFC app (VC++ 5.0 Enterprise). My program is running overnight, so it has to operate totally unattended. I need a way of trapping the error if the SQL DB is down and writing an error message to my app's log file.

How and where can I test if the ODBC connection was successful or failed ? In other words, where to test the result of the GetDefaultConnect procedure ?

Thanks a lot,

Derek
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Question by:der_bell
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msa092298 earned 100 total points
ID: 1323706
if you are using MFC CReocrdSet classes, you can catch exceptions of type CDBException and CMemoryException, the error information will be in the member variables.
You should use try..catch around nearly all CRecordSet and CDatabase methods which affect a connection (open, move, delete, close,etc...).
here's and example code
BOOL TryODBC (CDatabase &db,const char *SrcName,const char *UID,const char *pwd)
{
      try
      {
            CString s="";//"ODBC;";
            if (UID && *UID)
            {
                  s+="UID=";       s+=UID;
            }
            if (pwd && *pwd)
            {
                  if (UID && *UID) s+=";";
                  s+="PWD=";       s+=pwd;
            }
            s+=";DSN=";      s+=SrcName;
            if (db.OpenEx(s,CDatabase::useCursorLib | CDatabase::noOdbcDialog | CDatabase::openReadOnly))
                  return TRUE;
      }
      catch( CMemoryException* e )
      {
            m_errNum=3;
            e->Delete();
// log in your file here
            return FALSE;
      }
      catch( CDBException* e )
      {
            m_errNum=1;
            char s[10];     itoa(e->m_nRetCode,s,10);
m_errStr="\nTryODBC error : RetCode = ";                              m_errStr+="\n                  Error = ";                  m_errStr+=e->m_strError;
            m_errStr+="\n      StateNativeOrigin = ";  m_errStr+=e->m_strStateNativeOrigin;
            m_errStr+='\n';
                // log m_errStr here
            e->Delete();
            return FALSE;
      }
      catch( CException* e )
      {
            char s[1000];
            e->GetErrorMessage(s,1000);
            m_errStr=s;
            m_errNum=1;
            e->Delete();
      }
//connect failure
      m_errStr="Couldn't Connect";
      return FALSE;
}

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Expert Comment

by:msa092298
ID: 1323707
You should connect to the database source first and on success pass the CDatabase object to the constructor of CRecordSet to use that established connection.
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