用于查看已执行的sql的执行计划：

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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'));

....

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