AW: AW: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL v s. S tand ards

> > 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