Re: Counting propositions
Date: Tue, 22 Jun 2004 14:41:19 +0100
Message-ID: <CFWBc.19053$NK4.3265189_at_stones.force9.net>
x wrote:
> If there is something like count(distinct *) , it count "propositions"
> No matter how you modify the relation, it count "propositions"
> If you use count(distinct a,b,c) you count distinct (a,b,c) tuples no matter
> how you modify the relation (if a,b,c remains unaltered).
OK. But it's generally considered to be bad practice to use "select *" in production code; rather you should explicitly list all the columns. If you add an extra column it means the query needs changing possibly, but the advantages outweight the disadvantages I guess.
Isn't "select count(*)" a similar thing? You should explicitly name the data columns you want. If you change the candidate keys it may change the whole interpretation of the propositions. In which case it may no longer be true that you want to count propositions.
Maybe not the best of example but it's just for pedagogical purposes!
So the point you make above could be seen as an advantage just as much as a disadvantage.
Paul. Received on Tue Jun 22 2004 - 15:41:19 CEST