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* Some more weird NULL behavior
@ 2002-11-09 04:30 Ludwig Lim <lud_nowhere_man@yahoo.com>
2002-11-09 05:13 ` Re: Some more weird NULL behavior Stephan Szabo <sszabo@megazone23.bigpanda.com>
0 siblings, 1 reply; 2+ messages in thread
From: Ludwig Lim @ 2002-11-09 04:30 UTC (permalink / raw)
To: pgsql-sql
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.
However:
SELECT b FROM x WHERE a IS NULL returns 'LUDZ'
SELECT b from y WHERE a IS NULL returns 'TEST'
I also tried
SELECT x.b,y.b
FROM x,y
WHERE x.a = CAST(y.a AS INTEGER);
But it also returns zero rows.
Thank you in advance,
ludwig.
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^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Some more weird NULL behavior
2002-11-09 04:30 Some more weird NULL behavior Ludwig Lim <lud_nowhere_man@yahoo.com>
@ 2002-11-09 05:13 ` Stephan Szabo <sszabo@megazone23.bigpanda.com>
0 siblings, 0 replies; 2+ messages in thread
From: Stephan Szabo @ 2002-11-09 05:13 UTC (permalink / raw)
To: Ludwig Lim <lud_nowhere_man@yahoo.com>; +Cc: 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)
^ permalink raw reply [nested|flat] 2+ messages in thread
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2002-11-09 04:30 Some more weird NULL behavior Ludwig Lim <lud_nowhere_man@yahoo.com>
2002-11-09 05:13 ` Stephan Szabo <sszabo@megazone23.bigpanda.com>
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