SAS proc rank and its Oracle SQL equivalent

The following SAS rank and Oracle SQL produce the same results. In SAS, when there are ties, the average rank is used. To do the same in Oracle, we calculate the unique row numbers and then its average based on group id and variable (amt).

SAS rank.
proc rank data=tbl_in  out=tbl_out ties=mean descending;
by grp;
var amt;
ranks amt_rnk;
run;

Oracle SQL rank.
create table tbl_out
as with tbl as
(
select a.*,
row_number() over(partition by grp order by  amt  desc)  amt_rnk0  from tbl_in a
) select a.*, (avg( amt_rnk0  ) over(partition by  grp,  amt )) amt_rnk
  from tbl a;