Rich Hall <rhall(at)micropat(dot)com> writes:
> My question is why is the form
> "(anything) = NULL"
> allowed?
If you think it shouldn't be, you can turn on the transform_null_equals
flag. However, past experience has shown that that breaks more things
than it fixes. In any case, few people like to depend on such a
thoroughly nonstandard behavior ...
regards, tom lane