[postgis-users] ST_Difference geom with NULL

[Sandro Santilli]

On Sat, Sep 10, 2011 at 3:08 PM, aperi2007 <aperi2007 at gmail.com> wrote:
> Hi,
>
> using the postgis 2.00 svn ,
>
> I notice that the
> ST_Difference(geom,NULL)
> will return NULL.
>
> Instead
> ST_Difference(geom, EMPTY)
> will return the "geom" geometry
>
> Is this correct ?

I think it is.
NULL means "I don't know" while EMPTY means "I know it's nothing".

--strk;

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