Re: XOR logical operator

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 ...
>
>
>
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