I was getting duplicate hits of operator/route combinations.

>What exactly is wrong with result of the query?
>
>>
>>No, that didn't work. I seem to have cracked it with:
>>

>>...
>>  LEFT JOIN RF1 ;
>>    On	NET.Operator  == RF1.Operator ;
>>    and (    NET.Route == RF1.ERoute ;
>>      	 or EMPTY( RF1.ERoute) ) ;
>>...
>>

>>
>>>>Sorry Sergey, I don't understand. I'm not intending to do "strange experiments". Your reply is very vague. I told you originally had that clause in, and got wrong results, and this was before I was advised to LEFT JOIN.
>>>>
>>>>Is there a solution to this or is the whole thread too hard to understand?
>>>Try
>>>

>>>SELECT DISTINCT NET.Operator, NET.Route, NET.Start_Date, NET.End_Date, NET.RorF, NET.Passengers, ;
>>>	IIF( NET.Route == NET.Mcl_Rte, "    ", NET.Mcl_Rte) as ContrNum, NET.Family, ;
>>>	0000000 AS CurrPass, 0000000 AS PrevPass, op.Desc as OpDesc, ;
>>>	NVL(RF1.ServType, "?") as ServeType ;	
>>>  FROM NotETM NET ;
>>>    JOIN Operator op ;
>>>      On NET.Operator == op.Code ;
>>>    LEFT JOIN RF1 ;
>>>      On  NET.Operator == RF1.Operator ;
>>>      and NET.Route    == RF1.ERoute ;
>>>  WHERE (	 (	m.ldStartCurr BETWEEN NET.Start_date AND NET.End_date) ; ...
>>>