Oracle 11g Release 2

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create table test_table (Rid number, Id number);
Insert into test_table values (8100, 161);
1 rows affected

Insert into test_table values (8101,  2);
1 rows affected

Insert into test_table values (8102 ,  2);
1 rows affected

Insert into test_table values (8103  , 2);
1 rows affected

Insert into test_table values (8104 , 156);
1 rows affected

SELECT t2.rid
       , t2.id
       , DENSE_RANK() OVER (ORDER BY t2.max_rid)
FROM (
  SELECT MAX(t1.rid) OVER (PARTITION BY t1.grupa) AS max_rid
         , t1.rid
         , t1.id
  FROM (       
    SELECT rid
           , id
           ,ROW_NUMBER() OVER (ORDER BY rid) - ROW_NUMBER() OVER (PARTITION BY id ORDER BY rid) AS grupa
    FROM test_table) t1 )  t2
ORDER BY rid


RID
ID
DENSE_RANK()OVER(ORDERBYT2.MAX_RID)


8100
161
1

8101
2
2

8102
2
2

8103
2
2

8104
156
3