还是一样，

16:45:44 SQL> l

1  select  site_id,

2         count(*) sendnum

3  from

4  (select site_id,

5         ewb_no

6    from prod_send t

7    where scan_time >= to_date('2015-05-15', 'yyyy-mm-dd')

8     and scan_time < to_date('2015-05-16', 'yyyy-mm-dd')

9    group by site_id, ewb_no)

10* group by site_id

16:45:51 SQL> /

2793 rows selected.

Elapsed: 00:00:03.71

Execution Plan

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

Plan hash value: 652676349

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

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

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

|   0 | SELECT STATEMENT     |             |  3995 | 15980 |       |   162K  (1)| 00:32:36 |

|   1 |  HASH GROUP BY       |             |  3995 | 15980 |       |   162K  (1)| 00:32:36 |

|   2 |   VIEW               | VM_NWVW_0   |   437K|  1708K|       |   162K  (1)| 00:32:36 |

|   3 |    HASH GROUP BY     |             |   437K|    10M|    15M|   162K  (1)| 00:32:36 |

|*  4 |     TABLE ACCESS FULL| PROD_SEND  |   437K|    10M|       |   159K  (1)| 00:31:59 |

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

Predicate Information (identified by operation id):

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

4 - filter("SCAN_TIME">=TO_DATE(' 2015-05-15 00:00:00', 'syyyy-mm-dd

hh24:mi:ss') AND "SCAN_TIME"

hh24:mi:ss'))

Statistics

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

1  recursive calls

0  db block gets

586772  consistent gets

586762  physical reads

0  redo size

57840  bytes sent via SQL*Net to client

2570  bytes received via SQL*Net from client

188  SQL*Net roundtrips to/from client

0  sorts (memory)

0  sorts (disk)

2793  rows processed

单独执行里面的子句，也是走全表

16:48:21 SQL> l

1  select site_id,

2      ewb_no

3  from prod_send t

4   where scan_time >= to_date('2015-05-15', 'yyyy-mm-dd')

5   and scan_time < to_date('2015-05-16', 'yyyy-mm-dd')

6*  group by site_id, ewb_no

16:48:24 SQL> /

850824 rows selected.

Elapsed: 00:00:08.87

Execution Plan

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

Plan hash value: 2203583913

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

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

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

|   0 | SELECT STATEMENT     |             |   437K|    10M|       |   162K  (1)| 00:32:36|

|   1 |  HASH GROUP BY       |             |   437K|    10M|    15M|   162K  (1)| 00:32:36|

|*  2 |   TABLE ACCESS FULL  | PROD_SEND   |   437K|    10M|       |   159K  (1)| 00:31:59|

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

Predicate Information (identified by operation id):

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

2 - filter("SCAN_TIME">=TO_DATE(' 2015-05-15 00:00:00', 'syyyy-mm-dd

hh24:mi:ss') AND "SCAN_TIME"

hh24:mi:ss'))

Statistics

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

0  recursive calls

0  db block gets

586772  consistent gets

586762  physical reads

0  redo size

25943493  bytes sent via SQL*Net to client

624455  bytes received via SQL*Net from client

56723  SQL*Net roundtrips to/from client

0  sorts (memory)

0  sorts (disk)

850824  rows processed