> 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
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
In response to
pgsql-bugs by date
|Next:||From: Bruce Momjian||Date: 1999-10-26 17:44:02|
|Subject: Re: [BUGS] (null) != (null) ?|
|Previous:||From: Tom Lane||Date: 1999-10-26 16:23:53|
|Subject: Re: [BUGS] (null) != (null) ? |