Oracle not exists的等价写法

not exists可以改为left join + is null，可以看到改写前后执行计划一样，消耗资源一样，说明完全等价。SQL> drop table test purge;SQL> drop table test1 purge;
SQL> create table test as select * from dba_objects;
SQL> create table test1 as select * from dba_objects;
SQL> delete from test1 where rownum < 10;
SQL> commit;SQL> select count（1） from test t where not exists（
select 1 from test1 t1 where t1.object_id=t.object_id
）;
COUNT（1）
----------
11
SQL> select count（1） from test t,test1 t1 where t.object_id=t1.object_id（+）
and t1.object_id is null;
COUNT（1）
----------
11
SQL> select * from test t where not exists（
select 1 from test1 t1 where t1.object_id=t.object_id
）
minus
select t.* from test t,test1 t1 where t.object_id=t1.object_id（+）
and t1.object_id is null;
未选定行SQL> select t.* from test t,test1 t1 where t.object_id=t1.object_id（+）
and t1.object_id is null
minus
select * from test t where not exists（
select 1 from test1 t1 where t1.object_id=t.object_id
）;
未选定行SQL> set autotrace traceonly
SQL> select t.* from test t where not exists（
select 1 from test1 t1 where t1.object_id=t.object_id
）;
已选择11行。
执行计划
----------------------------------------------------------
Plan hash value: 2726816538
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost （%CPU）| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 72877 | 15M| | 1109 （1）| 00:00:16 |
|* 1 | HASH JOIN RIGHT ANTI| | 72877 | 15M| 1520K| 1109 （1）| 00:00:16 |
| 2 | TABLE ACCESS FULL | TEST1 | 61874 | 785K| | 196 （1）| 00:00:03 |
| 3 | TABLE ACCESS FULL | TEST | 72877 | 14M| | 197 （2）| 00:00:03 |
--------------------------------------------------------------------------------------
Predicate Information （identified by operation id）:
---------------------------------------------------
1 - access（"T1"."OBJECT_ID"="T"."OBJECT_ID"）
Note
-----
- dynamic sampling used for this statement （level=2）
统计信息
----------------------------------------------------------
7 recursive calls
0 db block gets
1142 consistent gets
0 physical reads
0 redo size
1577 bytes sent via SQL*Net to client
337 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts （memory）
0 sorts （disk）
11 rows processed
SQL> select t.* from test t,test1 t1 where t.object_id=t1.object_id（+）
2 and t1.object_id is null;
已选择11行。
执行计划
----------------------------------------------------------
Plan hash value: 2726816538
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost （%CPU）| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 72877 | 15M| | 1109 （1）| 00:00:16 |
|* 1 | HASH JOIN RIGHT ANTI| | 72877 | 15M| 1520K| 1109 （1）| 00:00:16 |
| 2 | TABLE ACCESS FULL | TEST1 | 61874 | 785K| | 196 （1）| 00:00:03 |
| 3 | TABLE ACCESS FULL | TEST | 72877 | 14M| | 197 （2）| 00:00:03 |
--------------------------------------------------------------------------------------
Predicate Information （identified by operation id）:
---------------------------------------------------
1 - access（"T"."OBJECT_ID"="T1"."OBJECT_ID"）
Note
-----
- dynamic sampling used for this statement （level=2）
统计信息
----------------------------------------------------------
7 recursive calls
0 db block gets
1142 consistent gets
0 physical reads
0 redo size
1577 bytes sent via SQL*Net to client
337 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts （memory）
0 sorts （disk）
11 rows processedOracle 单实例从32位迁移到 64位方法 http://www.linuxidc.com/Linux/2012-03/55759.htm在CentOS 6.4下安装Oracle 11gR2（x64） http://www.linuxidc.com/Linux/2014-02/97374.htmOracle 11gR2 在VMWare虚拟机中安装步骤 http://www.linuxidc.com/Linux/2013-09/89579p2.htmDebian 下安装 Oracle 11g XE R2 http://www.linuxidc.com/Linux/2014-03/98881.htmOracle导入导出expdp IMPDP详解 http://www.linuxidc.com/Linux/2014-04/99932.htmOracle 10g expdp导出报错ORA-4031的解决方法 http://www.linuxidc.com/Linux/2014-04/99842.htm更多Oracle相关信息见Oracle 专题页面 http://www.linuxidc.com/topicnews.aspx？tid=12本文永久更新链接地址