COMP3311 – Wk01

Just a couple random notes, to reiterate some things I need to become acquainted with. Definitely not comprehensive.

The ER Diagram

Cardinalities

1. Each manager manages exactly one branch, and each branch is managed by exactly one manager.
2. Each branch holds zero or more accounts, but each account is held be at most one branch.
3. Each customer owns zero or more accounts and each account is owned by zero or more customers.

Participation

Not all customers must take out a loan (or it is not the case that every customer takes out a loan), but every loan is taken out by at least one customer. i.e. Every loan is associated with at least one person, but every person is not necessarily associated with at least one loan.

Attributes Linked to Relationships

In (a) you know how much time a particular person spends on a project. In (b) you only know how much time has been spend on a particular project. You don’t know the distribution of that time among the researches that have worked on it.

References

Shepherd, John. COMP3311 09s1 Lecture Slides. http://www.cse.unsw.edu.au/~cs3311/09s1/lectures/. (Diagrams have also been sourced from here).

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