Pavel Menshchikov wrote:

> Kjell, could you give an example of an SQL statement (or whatever),
> which depends on three-state logic?

Sure:

select *
from MyTable
where NullableField = 'a'

select *
from MyTable
where NullableField <> 'a'

Without three-state logic, the two selects above would, in union, return
all rows. They won't, because rows with null in NullableField will not
be returned by either of then.

Kjell
--
--------------------------------------
Kjell Rilbe
Adressmarknaden AM AB
E-post: kjell.rilbe@...
Telefon: 08-761 06 55
Mobil: 0733-44 24 64