> > Thus it could be, that NULL in "where column = NULL" is not defined
> > to have a special meaning according to SQL92.
>
> The way I interpret Celko's interpretation of SQL92, that specific
> construct has a meaning; it evaluates to UNKNOWN, thus not to TRUE,
Imho the text refers to a content of a particular column of one particular row.
where table1.col1 = table2.col1
the content of table2.col1 is null --> comparison evaluates to UNKNOWN.
It does not state whether NULL is a valid constant expression.
Andreas
