Why is that? I've always been told that surrogate keys is best practise when it comes to designing databases. Natural keys are open to change and with surrogate keys you cut out some of the work with normalization (once you have 1NF you also have 2NF). Besides, it's basically spelled out in the assignment that they're supposed to use customer_ID as a primary key for Customers.

surrogate keys are fine, if you need them, and if they're appropriate, but only in the physical modelling stage of development

in the logical modelling stage (which is what ERDs are all about), you must use natural keys

any table with only a surrogate key, and no natural keys, is a disaster waiting to happen...

Are you sure the E-R diagram right?? Mine didnt have that much table...
like I didnt do the Company and branch table .....

Iam not sure about mine, i think company and branch are not needed. it just shows relation between branches and sales person.

I only did 7 tables......I dont get how you did yours.!
1-Product
2-Customer
3-Order
4-Saleperson
5-Territories
6-Material
7-Vendor

ok, Dont worry about tables, check whether the diagram meets all the requirements.
y dont u post ur ERD so that others can tell u how far ur ERD is correct!!
Jus an advice!!

I'm a bit confused here. I've always looked upon the design diagram as the logical design and the actual creation of the tables (via sql statements) as the physical design and nothing of what I've been told so far prevents you from using surrogate keys in the design model if you so wish. The one course I had in college taught us to look for natural keys as an exercise but then went on to say that surrogate keys was the better choice 9 times out of 10.

Isn't the Address-table a good example of such a table and isn't that a pretty common occurrence in a db?

surely the course made a distinction between logical and physical design?

ERDs are logical, i.e. no surrogate keys

it doesn't matter if you eventually end up using surrogate keys "9 times out of 10" in your physical tables

natural keys are not "an exercise"

they are a crucial part of proper logical design

if you fail to declare UNIQUE constraints in addition to your surrogate keys, you're going to be S.O.L. at some point

I wonder if I've got the definition of ERD wrong? The diagram that I'm working on (attached) is what I would refer to as a ERD. We also used to draw something called an Class Diagram in the inception phase were we just modelled entities in UML using Rational Rose, could this be what you're talking about?

It's particularly confusing when you read articles that say stuff like: