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Marshall wrote:
> On Mar 22, 4:19 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>> And if we had true physical independence, how much storage might the >> constant column occupy on disk?
Hi Marshall,
To declare the type of the column, you'll need some storage. That is, I think what your suggesting moves some of the space required 'out of the column values' and 'into the column definition'. If reckon that to store one of N types, you'll need at least log2(N) bits.
> This is possible because the number of bits needed to
> represent a value of a given type is the log2 of the number
> of possible values. Since T1 has 1 value, the number
> of bits needed is log2(1) = 0.
But there are now N extra types, and you'll need to store them somewhere.
>
> So the system can use 0 bits to store values of
> type T1. (Of course, it will need zero bits for each
> row, so we have to multiply the 0 by the number of
> rows to determine the total cost for the relation.)
>
:)
[...]
Cheers,
Joe
Received on Sun Mar 25 2007 - 06:26:10 CDT