IBE.SQL.EliteDBIO.updateVisitedBaseFromLog C# (CSharp) Method

        public void updateVisitedBaseFromLog(enVisitType Refresh)
        {
            String sqlString;
            
            try
            {
                if((Refresh & enVisitType.Systems) > 0)
                { 
                    sqlString = "insert into tbVisitedSystems(system_id, time)" +
                                "   select L1.system_id, L1.time " +
                                "      from tbLog L1 left join tbVisitedSystems V1 on L1.system_id = V1.system_id " +
                                "      where L1.system_id is not null " +
                                "      and   L1.time      > V1.time" +
                                "      and  not exists (select * from tbLog L2 " +
                                "                        where L1.system_id = L2.system_id" +
                                "                        and   L1.time      < L2.time)" +
                                "on duplicate key update time = L1.time";

                    Program.DBCon.Execute(sqlString);
                }

                if((Refresh & enVisitType.Stations) > 0)
                { 
                    sqlString = "insert into tbVisitedStations(station_id, time)" +
                                "   select L1.station_id, L1.time " +
                                "      from tbLog L1 left join tbVisitedStations V1 on L1.station_id = V1.station_id " +
                                "      where L1.station_id is not null " +
                                "      and   L1.time      > V1.time" +
                                "      and  not exists (select * from tbLog L2 " +
                                "                        where L1.station_id = L2.station_id" +
                                "                        and   L1.time      < L2.time)" +
                                " on duplicate key update time = L1.time";

                    Program.DBCon.Execute(sqlString);
                }

            }
            catch (Exception ex)
            {
                throw new Exception("Error while updating the visited systems from log", ex);
            }
        }