Re: why NOT NULL in PRIMARY key??

[Jochem van Dieten]

On 4/26/05, Jigal van Hemert wrote:
> http://dev.mysql.com/doc/mysql/en/silent-column-changes.html
> mentions that "Columns that are part of a PRIMARY KEY are made NOT NULL even
> if not declared that way. "
> 
> And http://dev.mysql.com/doc/mysql/en/create-table.html tells me that "A
> PRIMARY KEY is a unique KEY where all key columns must be defined as NOT
> NULL. If they are not explicitly declared as NOT NULL, MySQL declares them
> so implicitly (and silently). "
> 
> Why is this?

Because the SQL standard says so.

Jochem