|--Top(1) |--Bookmark Lookup(BOOKMARK:([Bmk1003]), OBJECT:([Northwind].[dbo].[Orders])) |--Index Seek(OBJECT:([Northwind].[dbo].[Orders].[OrderDate]), SEEK:([Orders].[OrderDate] IsNotNull) ORDERED BACKWARD)The second query produced this plan:
|--Bookmark Lookup(BOOKMARK:([Bmk1000]), OBJECT:([Northwind].[dbo].[Orders])) |--Nested Loops(Inner Join, OUTER REFERENCES:([Orders].[OrderDate])) |--Top(1) | |--Index Scan(OBJECT:([Northwind].[dbo].[Orders].[OrderDate]), ORDERED BACKWARD) |--Index Seek(OBJECT:([Northwind].[dbo].[Orders].[OrderDate]), SEEK:([Orders].[OrderDate]=[Orders].[OrderDate]) ORDERED FORWARD)So it looks like the optimizer has been trained to look for the first query and provided better performance. I'd stick with the first form.