I need to draw an ER (entity relation) diagram for the following situation:
there different types of loan available to employees which they may choose to take or not. They can take only 1 type of loan, or many types of loan, or even not take any. If they take a loan, then thay will start submitting payments after some time.
so i have made the ER diagram as following
(1) student <-----> (n) loan
(1) loan <-----> (n) payment
now i argue that a relation between "student" and "payment" is not necessary because given a payment we can uniqly identify the loan, and from a unique loan we then can uniqly identify the student.
anyway, some argue that on ER diagram i have to have also "student" <---> "payment" relation because the ER diagram is a business model and should not include programming logic ..
any opinions ? should i explicitly have that "student"<--->"payment" relation or not ? wouldn't it become just unnecessary data ?
thanks
2006-11-10 20:19:46 · 5 answers · asked by Zettag 2 in Computers & Internet ➔ Programming & Design
at the begining, the loan is available to students
sorry .. wrong typing
2006-11-10 20:25:02 · update #1
I'm not sure I completely understand your question, but I think I agree with including the student/payment relationship here. We draw an ER diagram from the problem description, and you said "they (meaning the student) will start submitting payments after some time".
2006-11-10 20:33:16 · answer #1 · answered by clueless_nerd 5 · 0⤊ 0⤋
Your logic on why it isn't necessary to have a relation between "student" and "payment", holds true if and only if you assume that no two students can take the same type of loan. If this assumption is false, then you would need a relation between "student" and "payment".
2006-11-10 20:38:36 · answer #2 · answered by simple_coder 2 · 0⤊ 0⤋
Depending on need of business process, the data model can be the relationship between student and payments:
students <--> (n) payments+loans
much faster, the rest will be the same.
2006-11-14 10:23:34 · answer #3 · answered by toodd 4 · 0⤊ 0⤋
This relationship ("student"<--->"payment") is evident from the other two transitively and may be dropped.
2006-11-10 20:36:05 · answer #4 · answered by jacinablackbox 4 · 0⤊ 0⤋
student
----------
studentid
studentName
payment
-----------
paymentid
fk_studentid
fk_loanid
paymentAmount
loan
-----
loanid
loanAmount
2006-11-10 21:13:02 · answer #5 · answered by Adeel I 3 · 0⤊ 0⤋