Dear Experts:
I am creating a very simple E-R model of retailing business.
Here is the scanario:
A customer places an order, which is recorded into Sale table. The Sale table should record of the customer and the employee who helped the sale.
The problem with which I need your help is:
The company's employees can also become clients.
How to display this recursive (or sub type-super type relations?) in an E-R diagram?
I spent quite much time trying to figure out.
If you may kindly show me a diagram, it will be tremendously appreciated.
Thanks!
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Thank you so much for your kind, prompt.
I am sorry for not responding sooner.
I am writing upon reading your kind tip.
Can you kindly take a look at the screen print below and to let me know whether
I am making a right approach?
I would like to learn the best possible E-R model from the given scenario.
Thanks again!
people
Genius, yes, I am finishing my assignment for a class. I am done except the recursive thing.
If my question violates the site policy, please feel free to delete my question.
I consulted with several books and spent many hours in online research before posting the question.
The recursive things are quite confusing. So far no one, including the authors of the books and the instructors, has explained it clearly.
Hope I clarified adequately.
Thanks.
I suggest you test GRayL's post: http:#a23587153
TO: bitter chicken:
YOU SAID: n practise, a FK on the 'clients' table, and a FK on the 'employees' table will link each record to the 'people' table, so a person can be an employee, a client, both, or neither.
MY QUESTION: May I understand that I need to create three entities: (1) super type People table and (2) two sub type tables: Customer and Employee. Should they share the same PK (e.g., PeopleID)?
Thanks!
Business Accounts
Answer for Membership
by: bitter_chickenPosted on 2009-02-08 at 18:12:08ID: 23586937
Either
a) create a single entity 'people' which represents both clients and employees; or
b) create a single abstracted entity 'people', then two entities related to that... 'clients' and 'employees', then a relationship from each 'clients' and 'employees' to 'sales'
In practise, a FK on the 'clients' table, and a FK on the 'employees' table will link each record to the 'people' table, so a person can be an employee, a client, both, or neither.
The 'people' table would include standard information (such as name, address), and the 'employee'/'client' tables would have information such as employee ID.
<can be> -- 1 [Employee] 1 -------<assists>
/ \
1 / \ n
[People] [Sales]
1 \ / n
<can be> -- 1 [Client] 1 -- <purchases>