Re: does a table always need a PK?

After takin a swig o' Arrakan spice grog, Christopher Browne <cbbrowne_at_acm.org> belched out...:
> A long time ago, in a galaxy far, far away, "Marshall Spight" <mspight_at_dnai.com> wrote:
>> So by extension, it's clear how one would handle the 'a*a-b*b+25' case:
>>
>> (a1*a1-b1*b1+25)+(a2*a2-b2*b2+25)+...+(an*an-bn*bn+25)
>>
>> I think that's a logical and consistent way to handle aggregates. Any
>> intra-tuple calculations are higher precedence than any inter-tuple
>> calculation. (Even if the happen to be the same operator, as in the
>> 'a+b' case.)
>
> Just so.
>
> It isn't necessarily TOTALLY irrational to consider applying reduction
> "inside the calculation," but it seems quite reasonable for the
> aggregates to be considered separately.

And by the way, it is probably more useful to use AVG()/AVERAGE()/MEAN() in these sorts of conversations, as that makes the issues more manifest. That will help answer how both COUNT() and SUM() should work since it is, in effect, something of a combination of them.

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