Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
5 consistent gets
0 physical reads
0 redo size
1850 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
9 rows processed
#优化方法2:
#增加函数索引，只让object_name IS NULL的保存在索引中
create index scott.idx_tb_sj01_02 on scott.tb_sj01(decode(object_name,null,1));
#原语句改写为：
select * from scott.tb_sj01 where decode(object_name,null,1)=1;
#优化后，COST=2，consistent gets=4
SQL> select * from scott.tb_sj01 where decode(object_name,null,1)=1;
9 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 612345449
----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 869 | 66044 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| TB_SJ01 | 869 | 66044 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IDX_TB_SJ01_02 | 9 | | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access(DECODE("OBJECT_NAME",NULL,1)=1)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
1850 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
9 rows processed
2.语句:select * from scott.tb_sj01 where object_name!='SJ'的优化
#优化前,COST=346，consistent gets=1246
SQL> select * from scott.tb_sj01 where object_name!='SJ';
11 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 283620643
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 79650 | 5911K| 346 (1)| 00:00:05 |
|* 1 | TABLE ACCESS FULL| TB_SJ01 | 79650 | 5911K| 346 (1)| 00:00:05 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("OBJECT_NAME"<>'SJ')
Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
1246 consistent gets
0 physical reads
0 redo size
1979 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
11 rows processed