Re: What predicates the following relation represents
Date: Thu, 01 Apr 2004 14:20:43 +0100
Mikito Harakiri wrote:
> PART SOLD
> ---- ---
> nuts 10
> nuts 15
> Is SALES a legal relation? Is database really a repository of facts?
It depends on the meaning given to the relation.
Suppose the predicate was:
"At some point in time, we have sold a batch of PART of size SOLD."
So the relation would be used for asking questions such as:
"Have we ever sold a batch of 7 nuts?" "Show me all the parts we have ever sold as a batch of 10" "Which is the most popular batch size for purchasers of nuts"
And your candidate key would be both columns.
Paul. Received on Thu Apr 01 2004 - 15:20:43 CEST