PK : Primary key
FK : Foreign key

These represent the fields on which the join will be performed. In the previous SELECT-SQL, the PK of the parent table (Inv) was joined with the FK of the child table (OnHand).

HTH

>>Try:
>>

SELECT Inv.Location, Count(OnHand.PK);
>>   FROM Inv;
>>   LEFT OUTER JOIN OnHand ON Inv.PK = OnHand.FK;
>>   GROUP BY Inv.Location

HTH
>
>Eh? What do the PK and FK represent?