CREATE TABLE OF_NUM
(
  OF_NUMBER  NUMBER(5,2)
);

Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.46);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.5);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.56);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.59);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.46);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.46);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.47);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.49);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.46);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.46);
Insert into OF_NUM
   (OF_NUMBER)
 Values
   (0.58);
COMMIT;

select distinct --OF_NUMBER , trunc(OF_NUMBER,1) ,
	   dense_rank() over (Order by  trunc(OF_NUMBER,1)    ) rnk ,
	   mIN(OF_NUMBER) over (partition by  trunc(OF_NUMBER,1)  ) MN,
	    max(OF_NUMBER) over (partition by  trunc(OF_NUMBER,1)  ) MX
from OF_num

SQL> select * from t order by weight, colour;
    WEIGHT COLOUR
---------- ------
       .46 D
       .46 E
       .46 F
       .46 F
       .46 G
       .47 F
       .49 G
        .5 F
       .56 E
       .58 F
       .59 D

11 rows selected.

SQL> select trunc(10*weight) grp, weight, colour 
  2  from t
  3  order by grp, colour, weight
  4  /
       GRP     WEIGHT COLOUR
---------- ---------- ------
         4        .46 D
         4        .46 E
         4        .46 F
         4        .46 F
         4        .47 F
         4        .46 G
         4        .49 G
         5        .59 D
         5        .56 E
         5         .5 F
         5        .58 F

11 rows selected.