Mike Christensen wrote on 22.06.2009 00:10:
I just tracked down a bug in my software due to an "unexpected" behavior
in Postgres.. Can someone clarify why this doesn't work (I haven't
tried it on MSSQL or anything else, so I'm not sure if this is the
official SQL standard or anything)..
CREATE TABLE test
(
value uuid
);
INSERT INTO test VALUES ('00000000-0000-0000-0000-000000000000');
INSERT INTO test VALUES ('11111111-1111-1111-1111-111111111111');
INSERT INTO test VALUES (null);
select * from test where value != '00000000-0000-0000-0000-000000000000';
What I expect to get is two rows: the
'11111111-1111-1111-1111-111111111111' row and the null row, as both
those values are in fact not '00000000-0000-0000-0000-000000000000'.
However, I only get the first one.
That is standard behaviour.
A comparison with a NULL value always returns false (and that is not a Postgres
speciality).
You need to use
select *
from test
where value != '00000000-0000-0000-0000-000000000000'
or value is null;
Thomas
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