can we apply self join on query result anf get max value??

here is my query...
select Max(OnDate) from abc a23 inner join (select max(OnDate) as OnDate1,ItemID,ProductName,price from( SELECT a.ItemId as ItemId,Im.ItemName as ProductName,(sb.TotalCost/sb.Quantity) as Price,Sbill.BillDate as OnDate FROM ((( SbillItem AS sb inner join (select Max(sb1.SBillId)as BillId,MAx(sb1.SupBillId) as SupplierBillId,sb1.ItemId as ItemId from SBillItem sb1 Group By sb1.ItemId) as a on a.SupplierBillId=sb.SupBillId and a.BillId=sb.SBillId and a.ITemId=sb.ITemId)inner join ItemMaster Im on im.ItemId=a.ItemId) inner join SupplierBill sbill on Sbill.SBillId=a.BillId) union all select s1.ItemId,Im.ItemName as ProductName, s1.Rate as Price,s1.OnDate as OnDate from ((Stock s1 inner join (select Max(s.StockId)as BillId ,s.ItemId as ItemId from Stock s Group By s.ItemId) as stk on stk.BillId=s1.StockId   and stk.ItemId=s1.ItemId)inner join ItemMaster Im on Im.ItemId=stk.ItemId)< ...