"paulruizendaal" <pnr@...> wrote:

>
> What are the opinions about this?

The Firebird behaviour violates the standard.

> What does the standard say?

"A table check constraint is satisfied if and only if the specified <search
condition> is not False for any row of
a table". And Unknown is not False.

> What do other databases implement?

PostgreSQL and MSSQL are standard compliant, i.e. they follow the Oracle's
line of thinking.


Dmitry