Re: Implementation of boolean types.

From: Tony Andrews <andrewst_at_onetel.com>
Date: 14 Jul 2005 02:50:11 -0700
Message-ID: <1121334611.925961.259350@o13g2000cwo.googlegroups.com>

Jonathan Leffler wrote:
> -CELKO- wrote:
> > SQL deliberately left out Booleans [...]
>
> SQL-1999 and SQL-2003 both have a BOOLEAN type, with recognized values
> TRUE, FALSE and UNKNOWN. I'm not clear whether NULL is equivalent to
> UNKNOWN or not; I've not scrutinized the weasel-words carefully enough.

What would we need UNKNOWN for when we already have NULL? NULL is all we have to mean both "inapplicable" and "missing/unknown" for all other data types in SQL, so why not for BOOLEAN? The differences seem rather subtle to me:

UNKNOWN - we know that we don't know whether this is true or false NULL - we don't know whether we know whether this is true or false?!

My head is spinning... Received on Thu Jul 14 2005 - 04:50:11 CDT