oracle in和exists、not in和not exists原理和性能探究(二)
ts其实是一样的，原理就是两张表做HASH JOIN SEMI。也可以通过10053事件看到两条sql语句最终转换成同一条sql。
not in和not exists原理及性能实验：
not exists 比 not in效率高的例子
SQL> select count(*) from test1 where object_id not in(select object_id from test2);
执行计划
----------------------------------------------------------
Plan hash value: 3641219899
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 4 | 81076 (2)| 00:16:13 |
| 1 | SORT AGGREGATE | | 1 | 4 | | |
|* 2 | FILTER | | | | | |
| 3 | TABLE ACCESS FULL| TEST1 | 1000 | 4000 | 5 (0)| 00:00:01 |
|* 4 | TABLE ACCESS FULL| TEST2 | 1 | 5 | 162 (2)| 00:00:02 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter( NOT EXISTS (SELECT /*+ */ 0 FROM "TEST2" "TEST2" WHERE
LNNVL("OBJECT_ID"<>:B1)))
4 - filter(LNNVL("OBJECT_ID"<>:B1))
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
9410 consistent gets
0 physical reads
0 redo size
407 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> select count(*) from test1 t1 where not exists
(select 1 from test2 t2 where t1.object_id=t2.object_id);
执行计划
----------------------------------------------------------
Plan hash value: 240185659
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 9 | 168 (3)| 00:00:03 |
| 1 | SORT AGGREGATE | | 1 | 9 | | |
|* 2 | HASH JOIN ANTI | | 3 | 27 | 168 (3)| 00:00:03 |
| 3 | TABLE ACCESS FULL| TEST1 | 1000 | 4000 | 5 (0)| 00:00:01 |
| 4 | TABLE ACCESS FULL| TEST2 | 50687 | 247K| 162 (2)| 00:00:02 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID")
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
717 consistent gets
0 physical reads
0 redo size
407 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
not in比not exists 效率高的例子
SQL> Set autotrace off
SQL> drop table test1 purge;
表已删除。
SQL> drop table test2 purge;
表已删除。
SQL> create table test1 as select * from dba_objects where rownum <=5;
表已创建。
SQL> create table test2 as select * from dba_objects;