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Thread: XOR logical operator

XOR logical operator

From
Nagib Abi Fadel
Date:
Is there a XOR logical operator in Postgresql, or a
function for XOR ??

I only found in the docs a Binary XOR (#).

I need to do the following checkup:
(field1 is NULL XOR field2 is NULL XOR filed3 is NULL)

i can't right it like this:
(
(field1 is NUll or field2 is NUll)
and (field1 is NUll or field3 is NUll)
and (field2 is NUll or field3 is NUll)
)

But if i have alot of fields :
field1,field2,...,field5
... this will take a hell of a time
I can write a function F1 that does the following:
if a field is NULL it will return 1
else it will return 0

then i can do:
(F1(field1) # F1(field2) # F1(field3) ...)


but i just wanted to see if XOR already exists ...



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Re: XOR logical operator

From
Pavel Stehule
Date:
Hello,

PostgreSQL hasn't logical operator XOR. But You can find it in cookbook
http://www.brasileiro.net/postgres/cookbook/view-recipes.adp?section_id=41&format=long

Regards
Pavel



On Fri, 17 Oct 2003, Nagib Abi Fadel wrote:

> Is there a XOR logical operator in Postgresql, or a
> function for XOR ??
>
> I only found in the docs a Binary XOR (#).
>
> I need to do the following checkup:
> (field1 is NULL XOR field2 is NULL XOR filed3 is NULL)
>
> i can't right it like this:
> (
> (field1 is NUll or field2 is NUll)
> and (field1 is NUll or field3 is NUll)
> and (field2 is NUll or field3 is NUll)
> )
>
> But if i have alot of fields :
> field1,field2,...,field5
> ... this will take a hell of a time
> I can write a function F1 that does the following:
> if a field is NULL it will return 1
> else it will return 0
>
> then i can do:
> (F1(field1) # F1(field2) # F1(field3) ...)
>
>
> but i just wanted to see if XOR already exists ...
>
>
>
> __________________________________
> Do you Yahoo!?
> The New Yahoo! Shopping - with improved product search
> http://shopping.yahoo.com
>
> ---------------------------(end of broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
>

Re: XOR logical operator

From
Peter Childs
Date:
On Fri, 17 Oct 2003, Nagib Abi Fadel wrote:

> Is there a XOR logical operator in Postgresql, or a
> function for XOR ??
>
> I only found in the docs a Binary XOR (#).
>
> I need to do the following checkup:
> (field1 is NULL XOR field2 is NULL XOR filed3 is NULL)

    Good idea. hmmm

CREATE FUNCTION xor(bool,bool) RETURNS bool AS '
SELECT ($1 AND NOT $2) OR (NOT $1 AND $2);
' LANGUAGE 'sql';

CREATE OPERATOR ~| (PROCEDURE='xor',LEFTARG=bool,RIGHTARG=bool);

    May not be all that neat but it does work so long as you use
brackets... I think improvements could be made. (10 minute job if that)

Peter Childs


>
> i can't right it like this:
> (
> (field1 is NUll or field2 is NUll)
> and (field1 is NUll or field3 is NUll)
> and (field2 is NUll or field3 is NUll)
> )
>
> But if i have alot of fields :
> field1,field2,...,field5
> ... this will take a hell of a time
> I can write a function F1 that does the following:
> if a field is NULL it will return 1
> else it will return 0
>
> then i can do:
> (F1(field1) # F1(field2) # F1(field3) ...)
>
>
> but i just wanted to see if XOR already exists ...
>
>
>
> __________________________________
> Do you Yahoo!?
> The New Yahoo! Shopping - with improved product search
> http://shopping.yahoo.com
>
> ---------------------------(end of broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
>

Re: XOR logical operator

From
Manfred Koizar
Date:
On Fri, 17 Oct 2003 01:04:48 -0700 (PDT), Nagib Abi Fadel
<nagib_postgres@yahoo.com> wrote:
>Is there a XOR logical operator in Postgresql

Yes: !=

Servus
 Manfred