On Mon, 28 Jan 2002 11:00:17 -0500, William Carson wrote: >Why doesn't R:Base (and some other programming languages) know that they >are not equal? Why do you need an IF vB IS NULL THEN when IF vA <> vB >THEN should suffice?
Bill, The ANSI standard for SQL says that a NULL cannot be compared to a non-null. Basically, an unknown value is neither "equal to" nor "not equal to" a known value. A null is not even equal to another null. This is that famous "three value logic" of SQL, which frustrates and confuses a few people enough that Microrim once gave in to their "whining" (scott: <grin>) and created the setting EQNULL, which you can use to make your application non-SQL complaint, but able to compare nulls to null. Bill ================================================ TO SEE MESSAGE POSTING GUIDELINES: Send a plain text email to [EMAIL PROTECTED] In the message body, put just two words: INTRO rbase-l ================================================ TO UNSUBSCRIBE: send a plain text email to [EMAIL PROTECTED] In the message body, put just two words: UNSUBSCRIBE rbase-l ================================================ TO SEARCH ARCHIVES: http://www.mail-archive.com/rbase-l%40sonetmail.com/
