Re: Lots of Idiotic Silly Braces?

Bob Badour wrote:
> paul c wrote:
...

>> The predicate somebody intends by this grouping could be "Shipment S 
>> included the set of parts {P}".  If we then ask "what combinations of 
>> parts have been shipped?", a knee-jerk reation might be to project 
>> away the S attribute:
>>
>> {P}:
>> {3,4}
>> {3}

I guess I was using the word "table" pretty casually. I'm fairly sure Codd didn't mention it much, talking rather of "normalization", and maybe I shouldn't suggest to compare the two, eg., he said:

"Normalization proceeds as follows. Starting with the relation at the top of the tree, take its primary key and expand each of the immediately subordinate relations by inserting this primary key domain or domain combination. The primary key of each expanded relation consists of the primary key before expansion augmented by the primary key copied down from the parent relation. Now, strike out from the parent relation all nonsimple domains, remove the top node of the tree, and repeat the same sequence of operations on each remaining subtree."

If I follow this literally, I suppose the fact that I can't "strike out ... all nonsimple domains", means that I am left with what I started with, namely a relation, you are saying that the table and relation in this case are one and the same, and you might say I am grasping at graphical representation that is an impossible over-simplification!

p Received on Mon Jul 16 2007 - 21:55:11 CEST