Theoretic question

[gazzieh]

Should the address of a customer be in a separate table to that customer's details?



My colleague and I have been discussing normalisation and database structure.

My argument is that the address depends upon the customer (it would not exist within the table unless the customer did) and that to apply Normalisation to this extent would lead to a need for separate tables for the County, Country, Postal Code, etc. The risk of duplication is low and the impact of an error would only impact upon that single customer anyway.

My colleague argues that this is unnecessary duplication and due to the rules of Normalisation this should be in a separate table (working to 3NF btw, no further).

Your views?

[alansidman]

You would only need to put the address in a separate table if there was the possibility of there being more than one address for the customer.

[gazzieh]

Ah, but this is the issue because there is always the factor that someone at the same address was a member of your club, etc.

My statement would be that though this were true the additional table is unnecessary and that this would be additional indexing that solves very little (the additional addressing would be most likely minimal and the number of times an address is likely to be repeated anyway would be 3 or 4 times maximum due to average household occupancy). As long as your system did not require a second address (making it a repeating field group) then the single address is a property of the named individual.

BTW, this is purely an academic argument and fun. We are very sad where I work; we find this kind of ting fun!