SELECT ... FROM DUAL ?

I have seen PL/SQL code (see
http://www.oracle.com/oramag/code/cod02189.html) such as:

         SELECT SUBSTR (vissuedt, 3, 3) INTO vmonth FROM dual;

my question is: would not this be more efficient written as:

       vmonth := SUBSTR(vissuedt,3,3);

Due to my understanding there is a small, but definate cost from switching from PL/SQL context to SQL context. I understand with things like sequences need to be selected from DUAL.

PL/SQL code I have seen and wanted to change right away:

    SELECT USER INTO v_username FROM dual;

    SELECT TRUNC(SYSDATE) INTO v_today FROM DUAL;

Perhaps I am just being picky.

Phil Bolduc
North Vancouver, Canada

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Share what you know. Learn what you don't. Received on Fri Sep 17 1999 - 02:40:42 CDT