What's the harm in a cupla dupes?

[Guest]

Regarding my backpacker hostel in Panama.

Is there any crime in allowing duplicates in my database? I mean, it's
really no big deal to me if I have 18 different Jessica Simpsons in my list
of clients, because if for whatever reason one day I want to differentiate
between them, I will also have passport and nationality info. Also, if it
is the same exact Jessica Simpson who is coming back for return visits, I
will be able to differentiate based on her dates of stay. (quite unlikely
that I will have 2 Jessica Simpsons on the same exact dates). Also, in my
business, it is infrequent that I would need to hold on to this detailed info
for more than a year, I am more interested in over all guest trends, money
totals and nationality counts than I am in individual names of clients,
especially after some time has passed.

 

[tina]

if you have 18 different Jessica Simpsons who are actually different
persons, then those 18 records are not duplicates; that's what primary keys
are for - to ensure the individuality of records that may otherwise have
identical, or nearly so, data.

if you want to enter the same Jessica Simpson in your database 18 times,
that's your outlook. it's a violation of normalization principles, which are
a tried and proven set of rules for relational data handling. but if you run
into problems with your data in the future due to violating those
guidelines, you're not hurting anyone but yourself, so you can certainly
suit yourself.

hth