How to check the execution plan of the Query

There are three ways to check the execution plan:
1) Using Cursor
2) Using AWR
3) Using explain plan set <sql>

1) Using Cursor:
============

Query:
=====
set lines 300 pages 300
select * from table(dbms_xplan.display_cursor('&sql_id'))
/

Input: SQL_ID

Output:

======

Plan hash value: 1357081020

----------------------------------------------------------------------------------

| Id  | Operation                 | Name | Rows  | Bytes | Cost (%CPU)| Time     |

----------------------------------------------------------------------------------

|   0 | SELECT STATEMENT          |      |       |       |     3 (100)|          |

|   1 |  TABLE ACCESS STORAGE FULL| TEST |     5 |   175 |     3   (0)| 00:00:01 |

----------------------------------------------------------------------------------

Note

-----

   - dynamic sampling used for this statement (level=2)

2) Using AWR:

Query:

======

set lines 300 pages 3000

select * from table(dbms_xplan.display_awr('&sql_id'))

/

Input: SQL_ID

Output:

=======

Plan hash value: 1357081020

----------------------------------------------------------------------------------

| Id  | Operation                 | Name | Rows  | Bytes | Cost (%CPU)| Time     |

----------------------------------------------------------------------------------

|   0 | SELECT STATEMENT          |      |       |       |     3 (100)|          |

|   1 |  TABLE ACCESS STORAGE FULL| TEST |     5 |   175 |     3   (0)| 00:00:01 |

----------------------------------------------------------------------------------

Note

-----

   - dynamic sampling used for this statement (level=2)

3) Using explain plan set <sql>  :

========================

Query:

======

SQL> explain plan for select * from test;

Explained.

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

Output:

=======

PLAN_TABLE_OUTPUT

-------------------

Plan hash value: 1357081020

----------------------------------------------------------------------------------

| Id  | Operation                 | Name | Rows  | Bytes | Cost (%CPU)| Time     |

----------------------------------------------------------------------------------

|   0 | SELECT STATEMENT          |      |     5 |   175 |     3   (0)| 00:00:01 |

|   1 |  TABLE ACCESS STORAGE FULL| TEST |     5 |   175 |     3   (0)| 00:00:01 |

----------------------------------------------------------------------------------

Note

-----

   - dynamic sampling used for this statement (level=2)