From: | "Ries van Twisk" <ries(at)jongert(dot)nl> |
---|---|
To: | "'Ajit Aranha'" <ajit_aranha(at)rocketmail(dot)com>, <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: Null not equal to '' (empty) |
Date: | 2002-09-27 12:40:06 |
Message-ID: | 000001c26623$02f515a0$f100000a@IT001 |
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Lists: | pgsql-sql |
This is because '' is not equal to NULL
'' Means a empty string
NULL means a empty set
So this: SELECT * FROM tbl WHERE c1 IS NULL;
is totally different then: SELECT * FROM tbl WHERE c1='';
Ries
-----Oorspronkelijk bericht-----
Van: pgsql-sql-owner(at)postgresql(dot)org
[mailto:pgsql-sql-owner(at)postgresql(dot)org]Namens Ajit Aranha
Verzonden: vrijdag 20 september 2002 8:09
Aan: pgsql-sql(at)postgresql(dot)org
Onderwerp: [SQL] Null not equal to '' (empty)
Why is ''(empty) not equal to null? Its a major headache when porting
from other RDBMS like Oracle. Anyone knows any easy workarounds?
i.e. if you use: create table tbl (
c1 varchar(5));
insert into tbl values ('');
select * from tbl where c1 is null; will return
zero rows.
Also try this: select TO_DATE('','DD-MM-YY'); and
this TO_DATE('','DD-Mon-YY');
;-)
-Ajit (ajit_aranha(at)rocketmail(dot)com)
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