Re: Working with NOR gates

Laconic2 wrote:

>
> Anyway, what if one were to generalize this concept from Boolean
> arithmetic to relations.
>
> What if I have this predicate? "The employee with emp_id 123 has a first
> name that is NOT 'FRED'". In the same relation,
> I have a predicate like this, "The employee with emp_id 123 has a first
> name
> that is NOT 'BILL'". Now the assertion of these two predicates together
> is like asserting "The employee with emp_id 123 has a first name that is
> NOT ('FRED' OR 'BILL')".
>
> Notice how I snuck the OR in there, without having a mechanism to express
> OR
> in relations to begin with. It's easier to think about this stuff if
> there are only a finite number of first names.
>

How do you see this coming in?

For instance, all searching of a db can be reduced to a few operations on lists of keys, right? Consider I have a list of every row in EMPLOYEES where first name = 'BILL', and another list for each value of first name, and another list for every value of every other column. Evaluating a filter on the table is going to come down to intersecting these sets, unioning them, or a set substraction or division.

Can the set operators be reduced to only one like the booleans? I had not thought so, but had not thought of it much actually.

-- 
Kenneth Downs
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