How do I use ROW_NUMBER()?

Question

I want to use the ROW_NUMBER() to get...

1. To get the max(ROW_NUMBER()) --> Or i guess this would also be the count of all rows

Answer 1

select 
  Ml.Hid,
  ml.blockid,
  row_number() over (partition by ml.blockid order by Ml.Hid desc) as rownumber,
  H.HNAME 
from MIT_LeadBechmarkHamletwise ML
join [MT.HAMLE] h on ML.Hid=h.HID