* 2008/06/25 星期三
*蒙昭良
*環境：WindowsXP + Oracle10gR2
*SQL的執行計劃
*/
SQL> select count(*) from test;

COUNT(*)
----------
     51470

SQL> set timing on
SQL> select count(*) from test;

COUNT(*)
----------
     51470

已用時間: 00: 00: 09.89
SQL> set autotrace on
SQL> select count(*) from test;

COUNT(*)
----------
     51470

已用時間: 00: 00: 03.78

執行計劃
----------------------------------------------------------
Plan hash value: 1950795681

-------------------------------------------------------------------
| Id | Operation          | Name | Rows | Cost (%CPU)| Time     |
-------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |     1 | 4107   (1)| 00:00:50 |
|   1 | SORT AGGREGATE    |      |     1 |            |          |
|   2 |   TABLE ACCESS FULL| TEST | 16763 | 4107   (1)| 00:00:50 |
-------------------------------------------------------------------

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

統計資訊
----------------------------------------------------------
          0 recursive calls
          0 db block gets
      15098 consistent gets
      12361 physical reads
          0 redo size
        410 bytes sent via SQL*Net to client
        385 bytes received via SQL*Net from client
          2 SQL*Net roundtrips to/from client
          0 sorts (memory)
          0 sorts (disk)
          1 rows processed

SQL的執行計劃

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