SQL & PL/SQL :: Distinct And Individual Records In Single Or Minimum Pass(es)

I have following data

select rowid,object_name,object_type from do;

ROWID OBJECT_NAME OBJECT_TYPE
------------------ ------------------------------ ------------------
AAA/wuAAHAAAW73AAA CON$ TABLE
AAA/wuAAHAAAW73AAB I_COL2 INDEX
AAA/wuAAHAAAW73AAC I_USER# INDEX
AAA/wuAAHAAAW73AAD C_TS# CLUSTER
AAA/wuAAHAAAW73AAE I_OBJ# INDEX
AAA/wuAAHAAAW73AAF I_CON2 INDEX

6 rows selected.

I want it in the following manner

select rowid,object_name,object_type from do;

ROWID OBJECT_NAME OBJECT_TYPEGROUP
------------------ ------------------------------ ---------------------------
AAA/wuAAHAAAW73AAA CON$ TABLE2
AAA/wuAAHAAAW73AAB I_COL2 INDEX1
AAA/wuAAHAAAW73AAC I_USER# INDEX1
AAA/wuAAHAAAW73AAD C_TS# CLUSTER1
AAA/wuAAHAAAW73AAE I_OBJ# INDEX1
AAA/wuAAHAAAW73AAF I_CON2 INDEX1

6 rows selected.

Here the GROUP is changing when the data type is changing and thus for same data type the group shall remain the same As of now this is achieved by - first selecting distinct object_type, then it's mod(rownum,<input variable) and this result of 'mod' is doing the grouping which is the retrieved along with rowid of all individual record

Present query is as following and it is not much efficient

SELECT DO.ROWID RWID, RID
FROM DO,
(
SELECT OT,CASE MOD(ROWNUM,:v) WHEN 0 THEN :v ELSE MOD(ROWNUM,:v) end as RID
FROM(
(SELECT DISTINCT OBJECT_TYPE OT

[code]....

I tried using sequence with cycle but it gave different results. Even I tried following but it did not gave satisfactory results

select d.rowid,d.object_type,x.x1 from do d,(select distinct object_type,mod(rownum,:v) x1 from do where
created>'01-jan-2008')x where d.object_type=x.object_type and created>'01-jan-2008';

In short the query needs Distinct with mod(rownum) and individual records in a single pass The mod(rownum) i.e. group shall change when the object_type changes but then shall remain constant through out the particular object_type.