with GetMissingItems(Rank, RowNumber, ItemNumber, UnitCost) as (
	select
		--RANK() over (order by ItemNumber, UnitCost) as Rank
		RANK() over (order by ItemNumber) as Rank
		, ROW_NUMBER() over (order by ItemNumber, UnitCost) as RowNumber
		, ItemNumber
		, UnitCost
	from MissingItems
)
select
	  ItemNumber
	, UnitCost
from GetMissingItems
where Rank = RowNumber

select
	  ItemNumber
	, min(UnitCost) 'UnitCost'
from #MissingItems
group by ItemNumber