Re: Null not equal to '' (empty)

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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