RE: fastest SQL?

From: Dunbar, Norman <norman.dunbar_at_environment-agency.gov.uk>
Date: Fri, 12 Mar 2010 08:37:19 -0000
Message-ID: <919FC80F27E0C6428106496EDF92A7520BE9C5AF_at_EXCCLUS05.PRODDS.NTNL>



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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Received on Fri Mar 12 2010 - 02:37:19 CST

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