| From: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
|---|---|
| To: | Ludwig Lim <lud_nowhere_man(at)yahoo(dot)com> |
| Cc: | PostgreSQL Mailing List <pgsql-sql(at)postgresql(dot)org> |
| Subject: | Re: Some more weird NULL behavior |
| Date: | 2002-11-09 05:13:43 |
| Message-ID: | 20021108210410.F19592-100000@megazone23.bigpanda.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-sql |
On Fri, 8 Nov 2002, Ludwig Lim wrote:
> Hi:
>
> I tried the following:
> CREATE TABLE x(
> a NUMERIC(5,0),
> b VARCHAR(5)
> );
>
> CREATE TABLE y(
> a INTEGER,
> b VARCHAR(5)
> );
>
> INSERT INTO x(b) VALUES ('LUDZ');
> INSERT INTO y(b) VALUES ('TEST');
>
> SELECT x.b,y.b FROM x,y WHERE x.a=y.a
> returns zero rows.
A comparison of two NULL values does not
return true, it returns unknown.
If you want to say equal or both null you
should do it explitly.
(x.a=y.a) or (x.a is null and y.a is null)
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