SQL Optimizer

From: Bob Robert <mssql_2002_at_yahoo.com>
Date: Mon, 10 Sep 2007 08:37:21 -0700 (PDT)
Message-ID: <854938.83868.qm@web63909.mail.re1.yahoo.com>

Could you please comment on the following SQL queries between Original SQL and Modified SQL. It seems that modified SQL's are perfoming better but I don't know how exactly Oracle optimizer works.

Original Query1:
 SELECT *
  FROM orders
 WHERE orders_updt_dtm BETWEEN sysdate - 7 AND sysdate
/

Modified Query1:
SELECT *
  FROM orders
WHERE 7 >= sysdate - orders_last_updt_dtm
/

Original Query2:
SELECT *
  FROM sales
WHERE sales_updt_dtm BETWEEN sysdate - 7 AND sysdate
/

Modified Query2:
SELECT *
  FROM sales
 WHERE sales_updt_dtm >= sysdate - 7 - 0    AND sales_updt_dtm <= sysdate - 0
/

Thanks,
Bob        

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Received on Mon Sep 10 2007 - 10:37:21 CDT