Entity Relationship Diagram

In summary: It seems redundant and unnecessarily complicated. Instead, you can simply show the relationship between Staff and Branch as a "manages" connection and leave it at that. This will also make your diagram clearer and easier to understand for others.
  • #1
bloynoys
25
0
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 separate 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.
ClassTest2-ERDAssignment1_zpsc9f0b594.png
 
Last edited:
Computer science news on Phys.org
  • #2
bloynoys said:
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 separate 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.
ClassTest2-ERDAssignment1_zpsc9f0b594.png
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?
 

1. What is an Entity Relationship Diagram (ERD)?

An Entity Relationship Diagram (ERD) is a visual representation of the relationships between different data entities in a database. It helps to organize and understand the structure of a database by showing how different pieces of data are related to each other.

2. What are the components of an ERD?

An ERD typically includes entities, attributes, and relationships. Entities represent a group of related information, attributes are characteristics of the entities, and relationships indicate how the entities are connected.

3. How is an ERD created?

An ERD is created using symbols and notation to represent the entities, attributes, and relationships. It can be drawn by hand or created using specialized software. The process involves identifying the entities and their attributes, and then determining the relationships between them.

4. What is the purpose of an ERD?

The purpose of an ERD is to provide a visual representation of the structure and relationships within a database. It helps to identify potential issues and inconsistencies in the database design, and serves as a blueprint for creating and maintaining a database.

5. How is an ERD useful in data modeling?

An ERD is an important tool in data modeling as it helps to identify the entities and relationships that are crucial to an organization's data. It also aids in identifying potential data redundancy and anomalies, and assists in creating a well-structured and efficient database design.

Similar threads

  • Set Theory, Logic, Probability, Statistics
2
Replies
35
Views
1K
  • Special and General Relativity
Replies
5
Views
1K
  • Programming and Computer Science
2
Replies
48
Views
9K
  • STEM Educators and Teaching
Replies
7
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
2
Views
3K
Writing: Input Wanted Number of Androids on Spaceships
  • Sci-Fi Writing and World Building
Replies
5
Views
97
  • Art, Music, History, and Linguistics
Replies
1
Views
998
Replies
10
Views
2K
  • Feedback and Announcements
Replies
0
Views
94K
Replies
1
Views
2K
Back
Top