SQL & PL/SQL

Hi,
i have one table in which most of the records are unique.
What would be better , to create index or to continue without index.

I need faster response of the query . No of rows in table is 32 lac.

below is the output with index and without index for some sample data.

in first scenario i have two indexes.
in second scenario i have only one index
in third one i don't have any index.

here col2 is having only 2-3 distinct values while both other columns are having almost unique values ( different data )

SQL> set autotrace traceonly
SQL> SELECT COUNT(*)
FROM my_table
WHERE col1 =28582
AND col2='1'
AND col3 ='1452631' ;

Elapsed: 00:00:00.47

Execution Plan
----------------------------------------------------------
Plan hash value: 2123134521

--------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 |16 | 3 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 |16 || |
|* 2 | INDEX RANGE SCAN| IND_my_table_1 | 1 |16 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

2 - access("col1"=28582 AND "col2"='1' AND
"col3"='1452631')


Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
3 consistent gets
0 physical reads
0 redo size
3882329993 bytes sent via SQL*Net to client
492 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> drop index Ind_my_table_1;

Index dropped.

Elapsed: 00:00:00.66
SQL> SELECT COUNT(*)
FROM my_table
WHERE col1 =28582
AND col2='1'
AND col3 ='1452631' ;

Elapsed: 00:00:01.52

Execution Plan
----------------------------------------------------------
Plan hash value: 2881393183

-------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 16 | 4(0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 16 | | |
|* 2 | TABLE ACCESS BY INDEX ROWID| my_table | 1 | 16 | 4(0)| 00:00:01 |
|* 3 | INDEX RANGE SCAN | IND_my_table_2 | 1 | | 3(0)| 00:00:01 |
-------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

2 - filter("col2"='1' AND "col3"='1452631')
3 - access("col1"=28582)


Statistics
----------------------------------------------------------
199 recursive calls
0 db block gets
31 consistent gets
2 physical reads
0 redo size
514 bytes sent via SQL*Net to client
492 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
6 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> drop index Ind_my_table_1 2;

Index dropped.

Elapsed: 00:00:00.07
SQL> SELECT COUNT(*)
FROM my_table
WHERE col1 =28582
AND col2='1'
AND col3 ='1452631' ;

Elapsed: 00:00:00.70

Execution Plan
----------------------------------------------------------
Plan hash value: 1679787526

---------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 16 | 6431(2)| 00:01:18 |
| 1 | SORT AGGREGATE | | 1 | 16 | | |
|* 2 | TABLE ACCESS FULL| my_table | 1 | 16 | 6431(2)| 00:01:18 |
---------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

2 - filter("col2"='1' AND "col1"=28582 AND
"col3"='1452631')


Statistics
----------------------------------------------------------
169 recursive calls
0 db block gets
29754 consistent gets
0 physical reads
0 redo size
514 bytes sent via SQL*Net to client
492 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
5 sorts (memory)
0 sorts (disk)
1 rows processed


Pl suggest how should i create the index.