oracle10gR2 中，用 in 还是用or的问题

最新推荐文章于 2025-02-20 08:43:06 发布

原创最新推荐文章于 2025-02-20 08:43:06 发布 · 1.7k 阅读

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#table #iterator #sql #access #disk

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本文通过实际案例对比了SQL中使用IN关键字与OR运算符进行多条件查询时的执行计划及性能差异，发现使用IN可以减少递归调用次数，提高查询效率。

select table_name from test where table_name='DBMS_ALERT_INFO' or table_name ='DBMS_APPS_UPG_WORKING';

执行计划
----------------------------------------------------------
Plan hash value: 2019477598

-------------------------------------------------------------------------------------
| Id | Operation         | Name            | Rows | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT |                 |    12 |   204 |     3   (0)| 00:00:01 |
|   1 | INLIST ITERATOR |                 |       |       |            |          |
|* 2 |   INDEX RANGE SCAN| IDX_TEST_TBNAME |    12 |   204 |     3   (0)| 00:00:01 |
-------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access("TABLE_NAME"='DBMS_ALERT_INFO' OR
              "TABLE_NAME"='DBMS_APPS_UPG_WORKING')

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

统计信息
----------------------------------------------------------
          5 recursive calls
          0 db block gets
         81 consistent gets
          0 physical reads
          0 redo size
        546 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)
         14 rows processed

select table_name from test where table_name in ('DBMS_ALERT_INFO','DBMS_APPS_UPG_WORKING');

执行计划
----------------------------------------------------------
Plan hash value: 2019477598

-------------------------------------------------------------------------------------
| Id | Operation         | Name            | Rows | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT |                 |    12 |   204 |     3   (0)| 00:00:01 |
|   1 | INLIST ITERATOR |                 |       |       |            |          |
|* 2 |   INDEX RANGE SCAN| IDX_TEST_TBNAME |    12 |   204 |     3   (0)| 00:00:01 |
-------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access("TABLE_NAME"='DBMS_ALERT_INFO' OR
              "TABLE_NAME"='DBMS_APPS_UPG_WORKING')

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

统计信息
----------------------------------------------------------
          4 recursive calls
          0 db block gets
         81 consistent gets
          0 physical reads
          0 redo size
        546 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)
         14 rows processed