how to update duplicate rows in a column to a new values - sql

Question

I will explain my problem briefly
have duplicate rino like below (actually this rino is the serial number in front end)
chqid rino branchid
----- ---- --------
876 6 2
14 6 2
18 10 2
828 10 2
829 11 2
19 11 2
830 12 2
20 12 2
78 40 2
1092 40 2
1094 41 2
79 41 2
413 43 2
1103 43 2
82 44 2
1104 44 2
1105 45 2
83 45 2
91 46 2
1106 46 2
here in my case I don't want to delete these duplicate rino instead of that I planned to update the rino having max date(column not specified in the above sample actually a date column is there) to the next rino number
what exactly I meant is :
if I sort out the above result according to the max(date) I will get
chqid rino branchid
----- ---- --------
876 6 2
828 10 2
19 11 2
830 12 2
1092 40 2
79 41 2
413 43 2
82 44 2
83 45 2
1106 46 2
(NOTE : total number of duplicate rows are 10 in branchid=2)
the last entered rino in the table for branchid=2 is 245
So I just want to update the 10 rows(Of column rino) with numbers starting from 246 to 255( just added 245+10 like this select lastno+ generate_series(1,10) nos from tab where cola=4 and branchid = 2 and vrid=20;)
Expected Output:
chqid rino branchid
----- ---- --------
876 246 2
828 247 2
19 248 2
830 249 2
1092 250 2
79 251 2
413 252 2
82 253 2
83 254 2
1106 255 2
using postgresql

Answer 1

Finally I found a solution, am using dynamic-sql to solve my issue
do
$$
declare
arow record;
begin
for arow in
select chqid,rino,branchid from (
select chqid,rino::int ,vrid,branchid ,row_number()over (partition by rino::int ) rn
from tab
where vrid =20
and branchid = 2)t
where rn >1
loop
execute format('
update tab
set rino=(select max(rino::int)+1 from gtab19 where acyrid=4 and branchid = 2 and vrid=20)
where chqid=%s
',arow.chqid);
end loop;
end;
$$;