//Desc: Ö´ÐвéѯÓï¾ä
function TDBConnManager.WorkerQuery(const nWorker: PDBWorker;
  const nSQL: string): TDataSet;
var nStep: Integer;
    nException: string;
begin
  Result := nWorker.FQuery;
  nException := '';
  nStep := 0;

  while nStep <= 2 do
  try
    if nStep = 1 then
    begin
      nWorker.FQuery.Close;
      nWorker.FQuery.SQL.Text := 'select 1';
      nWorker.FQuery.Open;

      nWorker.FQuery.Close;
      Break;
      //connection is ok
    end else

    if nStep = 2 then
    begin
      nWorker.FConn.Close;
      nWorker.FConn.Open;
    end; //reconnnect
    
    nWorker.FQuery.Close;
    nWorker.FQuery.SQL.Text := nSQL;
    nWorker.FQuery.Open;

    nException := '';
    Break;
  except
    on E:Exception do
    begin
      Inc(nStep);
      nException := E.Message;
    end;
  end;

  if nException <> '' then
  begin
    WriteLog('SQL: ' + nSQL + ' ::: ' + nException);
    raise Exception.Create(nException);
  end;
end;