SQL> create table index_test as select rownum a, rownum b from dual connect by level < 100000;

Table created.

SQL> create index index_test_idx on index_test(a);

Index created.

SQL> explain plan for select * from index_test where a in (1,50,200);

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------------
Plan hash value: 600866337

-----------------------------------------------------------------------------------------------
| Id  | Operation                    | Name           | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                |     2 |    52 |     5   (0)| 00:00:01 |
|   1 |  INLIST ITERATOR             |                |       |       |            |          |
|   2 |   TABLE ACCESS BY INDEX ROWID| INDEX_TEST     |     2 |    52 |     5   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN          | INDEX_TEST_IDX |   391 |       |     4   (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------


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

   3 - access("A"=1 OR "A"=50 OR "A"=200)

Note
-----
   - dynamic sampling used for this statement

19 rows selected.

SQL>