Re: BUG #5028: CASE returns ELSE value always when type is"char"

On Wed, Sep 2, 2009 at 3:34 PM, Sam Mason<sam(at)samason(dot)me(dot)uk> wrote:
> On Wed, Sep 02, 2009 at 12:54:03PM -0500, Kevin Grittner wrote:
>> Sam Mason <sam(at)samason(dot)me(dot)uk> wrote:
>> > If we did follow Kevin's request directly, should we also be
>> > specifying the type of NULL?
>>
>> I don't *think* the SQL standard requires that, and barring that I
>> don't see any compelling reason to type NULL.
>
> I've just realized that either I'm missing your point entirely (it's
> happened before :) or this ignores the point entirely.  PG wants to
> assign types to every expression, whether this expression will evaluate
> to a NULL value at run-time or not is immaterial in this regard.  I
> think SQL wants to do the same, but I don't have as much conviction as
> Tom here.  Once we're ascribing types to expressions then whether it
> happens to contain the literal "1", "'txt'" or "NULL" we're committed to
> giving it some type---the only question is which one.  We thus need to
> type expressions consisting of just NULL constants.
>
> A fun puzzle to base any inductive solution on is what type to ascribe
> to the following:
>
>  CREATE VIEW v (c) AS
>    SELECT NULL;

'a of course.

...Robert