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Entity Relationship Diagram

  1. Oct 2, 2014 #1
    I am doing a ER Diagram for a class and having a lot of trouble with a specific piece of the sentence. Anyway, here is the business requirements we are diagramming:

    The video rental company has several branches throughout the USA. The data held on each branch is the branch address made up of street, city, state, and zip code, and the many telephone numbers each branch has. Each branch is given a branch number, which is unique throughout the company. Each branch is allocated staff. Only one staff may manage many other staff members and may manage only one local branch. The data held on a member of staff is his or her name, position, and salary. A staff may work at more than one location. Each member of staff is given a staff number, which is unique throughout the company. Each branch has a stock of videos. A branch may not have all video titles. The data held on a video is the, video number, title, category, daily rental, cost, status, and the names of the main actors. Each video may have many actors. Before renting a video from the company, a customer must first register as a member of a local branch. The data held on a customer is the first and last name, address, and the date that the customer registered at a branch. Each member is given a customer number, which is unique throughout all branches of the company. Once registered, a member is free to rent many videos. The data held on each video rental is the rental number, the full name and number of the member, the video number, title, and daily rental, and the dates the video is rented out and date returned. The rental number is unique throughout the company.

    The piece highlighted is the piece I am having trouble with. My diagram is below. I believe that manage should be a seperate entity that needs to connect to both staff (that they manage) and branch (which they manage). Is this correct? Or is there a different way to diagram this that I am not thinking of. Image below.

    Last edited: Oct 2, 2014
  2. jcsd
  3. Oct 4, 2014 #2


    Staff: Mentor

    I don't believe that "Manage" should be an entity. All of your other entities are nouns (staff, branch, customers, orders, videos), and these entities interact with other entities via verbs (employs, contains, registers, etc.). You already show a "manage" connection between Staff and Branch, so why is it necessary to also have a Manage entity?
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