How to display the explain plan of an SQL statement

Use Autotrace in SQL*Plus.

SQL> SET AUTOTRACE TRACEONLY
SQL> SELECT * FROM dual;


Execution Plan
----------------------------------------------------------
Plan hash value: 272002086

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     1 |     2 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| DUAL |     1 |     2 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------


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

Use EXPLAIN PLAN FOR to store the plan for a SQL statement in PLAN_TABLE.

SQL> EXPLAIN PLAN FOR
     SELECT * FROM dual;

Explained.

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(format => 'ALL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 272002086

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     1 |     2 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| DUAL |     1 |     2 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / DUAL@SEL$1

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - "DUAL"."DUMMY"[VARCHAR2,1]

18 rows selected.


Execution Plan
----------------------------------------------------------
Plan hash value: 2137789089

---------------------------------------------------------------------------------------------
| Id  | Operation                         | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                  |         |  8168 | 16336 |    29   (0)| 00:00:01 |
|   1 |  COLLECTION ITERATOR PICKLER FETCH| DISPLAY |  8168 | 16336 |    29   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------


Statistics
----------------------------------------------------------
         25  recursive calls
         12  db block gets
        171  consistent gets
          0  physical reads
          0  redo size
       1326  bytes sent via SQL*Net to client
         59  bytes received via SQL*Net from client
          3  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
         18  rows processed