在select 中的where 中使用index
/* 2008/07/01 星期一
*蒙昭良
*环境：windowsXP + Oracle10gR2
*在select 中的where 中使用index
*/
1 在where中使用索引
SQL> set timing on
SQL> set autotrace on
SQL> drop index test_owner_index;
索引已删除。
已用时间: 00: 00: 02.01
没有使用索引之前：全表扫描花4.46秒
SQL> select count(*) from test where wner='RISENET';
COUNT(*)
----------
1350
已用时间: 00: 00: 04.46
执行计划
----------------------------------------------------------
Plan hash value: 1950795681
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 6 | 4110 (1)| 00:00:50 |
| 1 | SORT AGGREGATE | | 1 | 6 | | |
|* 2 | TABLE ACCESS FULL| TEST | 1052 | 6312 | 4110 (1)| 00:00:50 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("OWNER"='RISENET')
统计信息
----------------------------------------------------------
124 recursive calls
0 db block gets
15108 consistent gets
15087 physical reads
0 redo size
409 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
2 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> create index test_owner_index
2 on test(owner);
索引已创建。
已用时间: 00: 00: 04.57
使用索引之后：0.01秒
SQL> select count(*) from test where wner='RISENET';
COUNT(*)
----------
1350
已用时间: 00: 00: 00.01
执行计划
----------------------------------------------------------
Plan hash value: 1335201336
--------------------------------------------------------------------------------
------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------------
------
| 0 | SELECT STATEMENT | | 1 | 6 | 3 (0)| 00:0
0:01 |
| 1 | SORT AGGREGATE | | 1 | 6 | |
|
|* 2 | INDEX RANGE SCAN| TEST_OWNER_INDEX | 1052 | 6312 | 3 (0)| 00:0
0:01 |
--------------------------------------------------------------------------------
------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OWNER"='RISENET')
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
6 consistent gets
5 physical reads
0 redo size
409 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> spool off
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