RE: fastest SQL?
- From: "Dunbar, Norman" <norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx>
- To: <DonGranaman@xxxxxxxxxxxxxxx>, "ORACLE-L" <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 12 Mar 2010 08:37:19 -0000
Morning all,
>> Finally! A solid reason to upgrade to 11g! ;-)
I'm pretty certain fast dual was introduced at 10g. Basically, if you
select DUMMY (or *) from dual, you actually go to dual and read blocks.
If you select <something> from dual, you get fast dual instead and no
blocks read.
SQL> set autotrace on
SQL> select dummy from dual;
D
-
X
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=2 Card=1 Bytes=2)
1 0 TABLE ACCESS (FULL) OF 'DUAL' (TABLE) (Cost=2 Card=1
Bytes=2)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
3 consistent gets
0 physical reads
SQL> select 1 from dual;
1
----------
1
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=2 Card=1)
1 0 FAST DUAL (Cost=2 Card=1)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
0 consistent gets
0 physical reads
0 redo size
Cheers,
Norman.
Norman Dunbar
Contract Oracle DBA
CIS Engineering Services
Internal : 7 28 2051
External : 0113 231 2051
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