以下的文章主要主要是对Oracle数据获取的实际方式的测试，我们首先是通过建立典型的实验环境，来对Oracle数据获取的实际操作来进行详细的说明，以下就是文章的具体内容描述，望你浏览之后会有所收获。

首先建立实验环境

createtabletestasselect*fromdba_objectswhere0=1; 
createindexind_test_idontest(object_id); 
insertintotestselect*fromdba_objects 
whereobject_idisnotnullandobject_id>10000orderbyobject_iddesc; 
analyzetabletestcomputestatisticsfortableforallcolumnsforallindexes; 
TableAccessFull 
SQL>setautotracetrace; 
SQL>selectobject_idfromtest; 
setautotracetrace; 
selectobject_idfromtest; 
|Id|Operation|Name|Rows|Bytes|Cost(%CPU)|Time| 
1|TABLEACCESSFULL|TEST|58650|229K|239(1)|00:00:03| 

注意这是因为object_id列默认是可以为null的,如果修改成not null那么Oracle数据获取方式会变成什么方式?

IndexFastFullScan 
altertabletestmodify(object_idnotnull); 
selectobject_idfromtest; 
|Id|Operation|Name|Rows|Bytes|Cost(%CPU)|Time| 
1|INDEXFASTFULLSCAN|IND_TEST_ID|58650|229K|66(0)|00:00:01| 
IndexFullScan 
select/*+index(testind_TEST_ID)*/object_idfromtest; 
|Id|Operation|Name|Rows|Bytes|Cost(%CPU)|Time| 
1|INDEXFULLSCAN|IND_TEST_ID|58650|229K|240(1)|00:00:03| 
IndexRangeScan 
select/*+index(testind_TEST_ID)*/object_idfromtestwhereobject_id<68926; 
|Id|Operation|Name|Rows|Bytes|Cost(%CPU)|Time| 
1|INDEXRANGESCAN|IND_TEST_ID|57903|226K|237(1)|00:00:03 
SQL>selectobject_idfromtestwhererownum<11;INDEXFASTFULLSCAN 
OBJECT_ID 
68917 
68918 
68919 
68920 
68921 
68922 
68923 
68924 
68925 
68926 

已选择10行。

SQL>select/*+index(testind_TEST_ID)*/object_idfromtestwhererownum<11;INDEXFULLSCAN 
OBJECT_ID 
10001 
10002 
10003 
10004 
10005 
10006 
10007 
10008 
10009 
10010 

已选择10行。

select*fromtestwhererownum<2; 
.......69554....... 

其他的不关注只关注OBJECT_ID列 。