I was refering to your original select not your strange experiments..

>Yes, that was covered in the original message as:
>
>>>> IIF( NET.Operator == RF1.Operator ;
>>>> and NET.Route == RF1.ERoute, RF1.ServType, "?") as ServeType ;
>>>>
>>>>
>>>>but this didn't work cos, I presume, if it didn't meet the join criteria on the RF1 table those recs weren't considered. So I took out the
>>>>
>>>>
>>>> and NET.Route == RF1.ERoute ;
>>>>
>
>
>>Terry,
>>
>>You should compare it with previous select. If you did you would see that something is missing in the later.

>>      and NET.Route    == RF1.ERoute ;
>>

>>>
>>>I tried the LEFT JOIN and it seemed to be working, then I started getting spurious results on certain data. Compare this with the previous SQL below(er):
>>>

>>>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, ;
>>>	IIF( NET.Route == RF1.ERoute, RF1.ServType, "?") as ServeType ;	
>>>  FROM NotETM NET ;
>>>    JOIN Operator op ;
>>>      On NET.Operator == op.Code ;
>>>    LEFT JOIN RF1 ;
>>>      On  NET.Operator == RF1.Operator ;
>>>  WHERE (	 (	m.ldStartCurr BETWEEN NET.Start_date AND NET.End_date) ; ...
>>>

>>>
>>>In this case there is just 1 NotETM (NET) record that meets the criteria for each operator
>>>If we take Operator 54, it has an RF1 record for route 0604, with a servtype of " "
>>>and ..............................RF1 record for route 0608, with a servtype of "D"
>>>
>>>My results give 2 recs for each: 1 operator's with servetype of " " and "?" and the other's with
>>>servetype of "?" and "D", but the passengers field is the same number in each case, and so it gets counted twice.
>>>
>>>ALSO
>>>
>>>I have to run through another similar table ETMDATA (to later get some average values to apply to NotETM data)
>>>
>>>

>>>SELECT DISTINCT ET.Operator, ET.Route, ET.Class, ET.Date, ET.RorF, op.Desc as OpDesc, ;
>>>	IIF( ET.Route == RF1.ERoute, RF1.ServType, "?") as ServeType, ;	
>>>	IIF( ET.Route == ET.Mcl_Rte, "    ", ET.Mcl_Rte) as ContrNum, ET.Family, ;
>>>	SUM( IIF( BETWEEN( ET.date, ldStartCurr, ldEndCurr), ET.Number, 0000000)) AS CurrPass, ;
>>>	SUM( IIF( BETWEEN( ET.date, ldStartPrev, ldEndPrev), ET.Number, 0000000)) AS PrevPass ;
>>>  FROM ETMData ET ;
>>>    JOIN Operator op ;
>>>      On ET.Operator == op.Code ;
>>>    LEFT JOIN RF1 ;
>>>      On ET.Operator == RF1.Operator ;
>>>  WHERE (	  ( ET.date BETWEEN ldStartCurr and ldEndCurr) ;
>>>        OR ( ET.date BETWEEN ldStartPrev and ldEndPrev) ); ...
>>>

>>>
>>>but this, since I had to add the LEFT JOIN, now takes FOREVER. Obviously it's creating too big a dataset, or intermediate data, but I don't see why either code is taking so long or failing. I can't really trust this second SQL now.
>>>
>>>Any ideas what's wrong?
>>>
>>>REALLY appreciate it.
>>>
>>>Terry
>>>
>>>>You can use LEFT JOIN to get all records for the table on the left and NVL() to convrt NULLs to something else.
>>>>
>>>>>Please consider the SQL below.
>>>>>The NET table is linked to the Route/Family table (RF1) by Operator and Route keys combo.
>>>>>For each NET record I need to get its ServType code from the matching RF1 table rec.
>>>>>BUT some NET recs don't have a matching RF1 rec, but still need to be reported.
>>>>>
>>>>>originally I just included RF1.ServType in the selection fields but NET recs with no matching RF1 weren't being reported. So I included the IIF() below (in the bigger picture)
>>>>>
>>>>>

>>>>>    IIF(    NET.Operator == RF1.Operator ;
>>>>>        and NET.Route    == RF1.ERoute, RF1.ServType, "?") as ServeType ;	
>>>>>

>>>>>
>>>>>but this didn't work cos, I presume, if it didn't meet the join criteria on the RF1 table those recs weren't considered. So I took out the
>>>>>
>>>>>

>>>>>      and NET.Route    == RF1.ERoute ;
>>>>>

>>>>>
>>>>>from the join but now get duplicated instances. Bit flummoxed at the moment. ANy ideas?
>>>>>
>>>>>'ppreciate it.
>>>>>
>>>>>

>>>>>SELECT 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, ;
>>>>>       IIF(    NET.Operator == RF1.Operator ;
>>>>>	  and NET.Route    == RF1.ERoute, RF1.ServType, "?") as ServeType ;	
>>>>>  FROM NotETM NET ;
>>>>>    JOIN Operator op ;
>>>>>      On NET.Operator == op.Code ;
>>>>>    JOIN RF1 ;
>>>>>      On  NET.Operator == RF1.Operator ;
>>>>>      and NET.Route    == RF1.ERoute ;
>>>>> WHERE (	 ( m.ldStartCurr BETWEEN NET.Start_date AND NET.End_date) ;
>>>>>        ...
>>>>>
>>>>>