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@postgresql.org
[mailto:pgsql-sql-owner@postgresql.org]Namens Ajit Aranha
Verzonden: vrijdag 20 september 2002 8:09
Aan: pgsql-sql@postgresql.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@rocketmail.com)
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