Re: "= null" & "is null"

When using other than "is null" or "is not null", Oracle does not return error but it seems to me that it always returns false like "1 = 2".

Thomas Kyte <tkyte_at_us.oracle.com> wrote:
: A copy of this was sent to Norris <johnnie_at_cooper.com.hk>
: (if that email address didn't require changing)
: On 26 Aug 1999 11:40:22 GMT, you wrote:

:>What is the difference between = null and is null?
:>
:>-- 

: the major difference is that "is null" will alway evaluate to either TRUE or
: FALSE whereas "= null" will NEVER evaluate to TRUE OR FALSE (it is unknown).

: Consider:

: tkyte_at_8.0> select * from dual where null is null;

: D
: -
: X

: tkyte_at_8.0> select * from dual where null = null;

: no rows selected

: tkyte_at_8.0> select * from dual where null != null;

: no rows selected

: It is almost always an error (cannot think of a case where it is not an error)
: to say " = null"

: --
: See http://govt.us.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'...
: Current article is "Part I of V, Autonomous Transactions" updated June 21'st
:
: Thomas Kyte tkyte_at_us.oracle.com
: Oracle Service Industries Reston, VA USA

: Opinions are mine and do not necessarily reflect those of Oracle Corporation

--
--
http://www.washington.edu/pine/faq/ Received on Thu Aug 26 1999 - 07:25:26 CDT