Re: NULLs: theoretical problems?

"Neo" <neo55592_at_hotmail.com> wrote in message news:1187641160.234792.278400_at_i38g2000prf.googlegroups.com...
>> > ... NULLs ... There are better and more consistent ways
>> > of describing missing values.
>>
>> Will you please elaborate on those methods you
>> consider better and more consistent? Thank you.
>
> Dbd, a lightweight db that represents things by creating a network of
> nodes (each equiv to an AND gate), has an alternative method of
> dealing with NULLs. It is simply, don't create nodes to signify that
> something is unknown because their absence already implies it.
>
> Suppose we store a person named john whose age is 30. Later, we want
> to store a person named mary but her age is unknown. In RMDB, we can
> 1) Refuse to enter a tuple for mary.
> 2) Enter a tuple for mary but incurr a NULL for age.
> 3) Redesign schema, add table T_PersonAge, move data, update code/
> queries, etc to avoid NULL.
>

4) Have the right schema to start with so that no problem arises.

-- 
David Portas, SQL Server MVP

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