Re: [GENERAL] PB with Null string

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At 11:26 +0200 on 23/12/98, darold wrote:


> I have tried this query to check if a field is empty:
>
>     SELECT * FROM t_table WHERE s_string='';
>
> where s_string is declared as text. But this doesn't work, why? Is
> there's an
> other way to do that ? I have also tried with NULL but I think it is not
> included
> in the 6.3.2...

There is a difference between the empty string and NULL. NULL means there
is no value in the field. The empty string means there is a value, and this
value is ''.

To check for nulls, you don't write s_string=NULL. This, unfortunately,
doesn't work in Postgres, because two NULLs are not considered equal. What
you should do is s_string IS NULL:

SELECT * FROM t_table WHERE s_string IS NULL;

Herouth

--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma