Re: why NOT NULL in PRIMARY key??

[Jochem van Dieten]

On 4/26/05, Jigal van Hemert wrote:
> From: "Jochem van Dieten"
>>> Why is this?
>>
>> Because the SQL standard says so.
> 
> A true observation, but still no explanation or reason why ;-P

I consider it a good enough explanation of why MySQL doesn't allow it.

As to why the SQL standard doesn't allow it: NULL doesn't fit
particularly well in relational theory and there has probably been
considerable pressure from certain vendors (imagine the problems when
an empty string is indistinguishable from a NULL so both '' = '' and
NULL <> NULL must be true, but now not just for some wacky varchar but
for your primary key).

Just speculation of course :)

Jochem