SQL> create table t2 as select * from dba_objects;

表已创建。

已用时间:  00: 00: 00.81

SQL> insert into t2 select * from t2;

已创建72695行。

已用时间:  00: 00: 00.98

SQL> insert into t2 select * from t2;

已创建145390行。

已用时间:  00: 00: 00.71

SQL> insert into t2 select * from t2;

已创建290780行。

已用时间:  00: 00: 02.40

SQL> commit;

提交完成。

已用时间:  00: 00: 00.00

SQL> select * from t2 where object_id=99;

已选择8行。

已用时间:  00: 00: 00.03

执行计划

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

Plan hash value: 1513984157

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

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

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

|   0 | SELECT STATEMENT  |      |    91 | 18837 |  2250   (1)| 00:00:27 |

|*  1 |  TABLE ACCESS FULL| T2   |    91 | 18837 |  2250   (1)| 00:00:27 |

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

Predicate Information (identified by operation id):

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

   1 - filter("OBJECT_ID"=99)

Note

-----

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

统计信息

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

          5  recursive calls

          0  db block gets

       8331  consistent gets

          0  physical reads

          0  redo size

       1774  bytes sent via SQL*Net to client

        519  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          8  rows processed

SQL> create index idx_t2_object_id on t2(object_id);

索引已创建。

已用时间:  00: 00: 00.73

SQL> select * from t2 where object_id=99;

已选择8行。

已用时间:  00: 00: 00.01

执行计划

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

Plan hash value: 188336643

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

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

| Id  | Operation                   | Name             | Rows  | Bytes | Cost (%

CPU)| Time     |

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

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

|   0 | SELECT STATEMENT            |                  |     8 |  1656 |    12

 (0)| 00:00:01 |

|   1 |  TABLE ACCESS BY INDEX ROWID| T2               |     8 |  1656 |    12

 (0)| 00:00:01 |

|*  2 |   INDEX RANGE SCAN          | IDX_T2_OBJECT_ID |     8 |       |     3

 (0)| 00:00:01 |

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

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

Predicate Information (identified by operation id):

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

   2 - access("OBJECT_ID"=99)

Note

-----

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

统计信息

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

          9  recursive calls

          0  db block gets

         90  consistent gets

          2  physical reads

          0  redo size

       2236  bytes sent via SQL*Net to client

        519  bytes received via SQL*Net from client

          2  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

          8  rows processed