Re: Demo: Modelling Cost of Travel Paths Between Towns

On 13 Nov 2004 11:03:13 -0800, Neo wrote:

(snip)
>> Philadelphia PA 19104 6/1/1682 11/12/2004
>> Neodelphia PA 19104 11/12/2004 12/31/2999
>>
>> And, no - storing PA twice is not redundant.
>
>Storing any thing (ie PA) twice is redundant.

Hi Neo,

A computer represents PA as a string of bits - either 16 or 32 bits on most modern computers. If you store PA twice, you have the same string of bits in two locations.

If you store PA once, you'll have to replace PA in the above rows with a pointer to that location. A computer represents a pointer as a string of bits - either 16 or 32 bits on most modern computers. So even if you store PA once, you still end up with the same string of bits in two locations.

> On way to prove
>redundancy is to change the second PA and see if data is corrupted
>(without triggers/code to synchronize them).

Changes to the data should reflect changes in the reality. If PA state boundaries are changed at the same moment that Philadelphia is renamed to Neodelphia, changing the second PA would in fact even be required.

Changing PA when the state boundaries don't change will of course trash your data, regardless of how you store it and how many times you store it. Even if I had just one row of data and then change PA to IL, it'll still be faulty.

> Also, if a property is
>added to PA, will you add it the first PA, second PA, or both?

You are -once again- showing your total lack of comprehension of normalization. If a propert is added to PA, it should be added in a seperate table.

Best, Hugo

-- 

(Remove _NO_ and _SPAM_ to get my e-mail address)