> SELECT r IS NULL, r IS NOT NULL
> FROM (VALUES (1,NULL)) r(a,b);
>
> returns FALSE for *both* columns. How can a row be both NULL *and*
> non-NULL?
Actually, the value is neither NULL, nor non-NULL.
Part of it is NULL and part of it isn't so neither "IS NULL" is true,
nor is "IS NOT NULL"
cheers,
WBL
On Wed, Jul 29, 2009 at 3:40 PM, Sam Mason<sam@samason.me.uk> wrote:
> On Wed, Jul 29, 2009 at 01:15:27PM +0000, Jasen Betts wrote:
>> On 2009-07-23, Sam Mason <sam@samason.me.uk> wrote:
>> >
http://www.postgres.cz/index.php/PostgreSQL_SQL_Tricks#Attention_on_IS_NULL_and_IS_NOT_NULL_operators_for_composite_types
>> >
>> > is scary; even worse is that it was changed to be like this in 8.2
>> > because the standard says it should behave this way. What on earth were
>> > they thinking when they defined the standard this way?
>>
>> since any comparson involving those tuples will return NULL true is the
>> correct value for IS NULL
>
> I think you missed the point:
>
> SELECT r IS NULL, r IS NOT NULL
> FROM (VALUES (1,NULL)) r(a,b);
>
> returns FALSE for *both* columns. How can a row be both NULL *and*
> non-NULL?
>
>> if you are bothered by this behavior you are misusing NULL.
>
> I understand that this is the specified behavior, and hence PG is
> correctly following the spec--but it still bothers me.
>
> --
> Sam http://samason.me.uk/
>
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