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An Introduction to Database Design


An Introduction to Database Design

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suntec
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Its an awesome article I came across in recent past for freshers. I have suggested many freshers to see this article for understanding the table design.

Nice example to demonstrate the complete idea of designing table.

Great Work!!!
sharath.chalamgari
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Good Work Paul!


I haven't seen any article that explains the database designing concepts like a story,easy to understand format. :-)
Chris Houghton
Chris Houghton
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Nice work!! It's often said that to truly understand a concept you should be able to explain it to others in simple terms and you've definitely done that with this article. Simplicity to the point of brilliance. I shall refer to this when explaining database design concepts to customers.
kenambrose
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I believe there are some serious flaws in this article. For example, recepts represent a historical record of a transaction occuring in a moment in time.

If one normalizes the customer as is done in this example, and simply uses a foreign key in each receipt, what happens if a customer changes their address at some later time? or name? (people do get married).

Now, ALL of the historical receipts return the NEW address or customer name, not the address or name of record at the time of the sale.

This can't be correct, and would get most businesses in serious legal trouble. And I personally have seen this type of nonsense in many amateurish attempts at normalization.

This presentation is oversimplified to the point of providing poor instruction I am afraid...



kenambrose
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I should dd that bob's original paper receipts were MORE accurate than the DB design offered. At least the paper receipts would always return accurate info for the customer for the moment in time the sale was completed....



mike_walsh
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Ken - I think you missed the "An Introduction". You bring up some points that would be a good follow on article. Why don't you write up an article that follows on to Paul's but adds some more advanced concepts and continues to explain them in a simple way. I'd love to see a part two.

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casinc815
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Paul:

Great primer. Showed it to some of my staff and have been able to raise the curiosity level so we can move away from spreadsheets. Once again, great article.

Jim
kenambrose
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re. Inroduction. Well I suppose it depends on what you feel are the "fundamentals" of our work in DB design. Personally, concepts such as natural business keys (the author jumps right into physical issues ala surrogate keys and misses this concept completely), historical record keeping concepts, etc. ARE the fundamentals, from my experience as a trainer.

I just think this is a primer based on someone's mixing up physical with conceptual and logical DB issues- a serious flaw that is the bane of our industry in my opinion...

ken



mtassin
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kenambrose (1/18/2011)
I believe there are some serious flaws in this article. For example, recepts represent a historical record of a transaction occuring in a moment in time.

If one normalizes the customer as is done in this example, and simply uses a foreign key in each receipt, what happens if a customer changes their address at some later time? or name? (people do get married).



This isn't an instruction manual to type 2 SCDs, I'd consider this a typical approach to an OLTP system. The whole purpose of a database like this is that if a customer's data changes that we minimize updates to correct data.

If Paul were writing an article on the basics of designing a data warehouse, then he could cover handling the type 2 SCD here in the ETL process, though I think this would be over Bob's head.

But I've seen too many multi-million dollar ERP databases handle this sort of customer record as "present value" exactly this way to completely discount it.

And if the customer data has changed enough, a new customer record could be created with a foreign key chaining in the same table to point the old record to the new.



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kenambrose
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re. new customer record. And there is no unique index on the business key. So as a result, an unlimited number of exact duplicate customer records could also be created from the design.

I don't know about you but that is exactly the type of nonsense I see repeatedly in the field when people who do not understand the basic concepts of DB design attempt it.

My statement stands. Bob's orignal paper record keeping is more accurate than the DB design presented...



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