通过dbms_xplan.display_cursor来获取执行计划

用于查看已执行的sql的执行计划：

 

SQL> select count(*) from abc;

  COUNT(*)
----------
        10

SQL> select sql_id from v$sql where sql_text='select count(*) from abc';

SQL_ID
-------------
crrfjnb0y4mq1

SQL> select * from table(dbms_xplan.display_cursor('crrfjnb0y4mq1'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID  crrfjnb0y4mq1, child number 0
-------------------------------------
select count(*) from abc

Plan hash value: 1045519631

-------------------------------------------------------------------
| Id  | Operation          | Name | Rows  | Cost (%CPU)| Time     |
-------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |       |     2 (100)|          |
|   1 |  SORT AGGREGATE    |      |     1 |            |          |

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|   2 |   TABLE ACCESS FULL| ABC  |    10 |     2   (0)| 00:00:01 |
-------------------------------------------------------------------

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

18 rows selected.

另外种灵活设置

select /*+gather_plan_statistics */ count(0) from abc

select * from table(dbms_xplan.display_cursor('crrfjnb0y4mq1',null,'all iostats last'));

....