> On Tue, 26 Oct 1999, Tom Lane wrote:
>
> : > Both "fieldname" definitions are identical (verified with char(2) and
> : > varchar(100) in particular), and both tables contain a row with a "null" in
> : > that field. However, the results don't contain the row with the "null"
> : > value.
> :
> : NULL = NULL does not yield TRUE, it yields NULL. For that matter,
> : NULL != NULL does not yield FALSE --- it yields NULL. This is a
> : basic consequence of the semantics of NULL.
>
> !?
>
> I have been using such constructs on commercial databases for ages. Do you
> have a link to a web-based SQL standard transcription that I could look this
> up? (I'll check up on exactly which database(s) I can use this type of
> construct when I get back to work tomorrow....)
>
> It seems _extremely_ counter-intuitive, especially in cases where both
> fields are in fact the same type.
But NULL is unknown. How do you know they are equal if both values are
unknown?
--
Bruce Momjian | http://www.op.net/~candle
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