RE: select count(*)

Sarma,
 
    Before you run the statement in each instance try setting "set
autotrace on".  That should give you your answer.
 

  
Dick Goulet, Senior Oracle DBA

45 Bartlett St  Marlborough, Ma 01752, USA
Tel.: 508.573.1978 |Fax:  508.229.2019 | Cell:508.742.5795 

RGoulet@xxxxxxxxxx
: POWERING TRANSFORMATION 

 

________________________________

From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Sarma Aryasomayajula
Sent: Friday, October 06, 2006 11:10 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: select count(*)



Hi!


 
I'm running the below query in PROD(10g R1) and ACPT(10g R2). the query
returns in fraction of a second in PROD and, If I run the same query in
ACPT, it's taking 30+ mins.
 
In Prod
S5UVAD@powls01 <mailto:S5UVAD@powls01>  > set timin on 
S5UVAD@powls01 > select count(*) from wlcbs_master.rpt_08_vew where 0=1;
 
  COUNT(*)
----------
         0
 
Elapsed: 00:00:00.07
S5UVAD@powls01 > sho user
 
In ACPT:
 
N7OTHA@AOWLS01 > set timin on
N7OTHA@AOWLS01 > select count(*) from rpt_08_vew where 0=1;
 
  COUNT(*)
----------
         0
 
Elapsed: 00:31:02.27

1. If I apply condition "where 0 = 1" on a single table, does oracle
reads 
entire table then applies this condition or otherwise since this is
negative 
condition does it apply without reading the entire table?

2. If the same condition is applied on a view which is join of 3 big 
tables(paritioned)? How does oracle executes the query?

Can any one explain the above scenarious.

Regards,

Sarma







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