Explain why the entity relationship (ER) model is useful. How has it helped to produce a more structured relational database design environment?

The ER Model was developed by Edgar F Codd in 1970 and since then, most people have used this model for designing databases. It helps us to understand how data should be stored in different tables of our database. In addition, we can also use the ER model to get an idea about what kind of queries will run on a table or between two tables.

The Entity Relationship Diagram consists of entities, attributes, relationships. An example would be :-

Entity: A noun that represents something which exists independent of other things; like person, place etc. Attributes are adjectives describing properties or characteristics of an entity e.g., name, age, height. Relationships represent actions taking place among entities and they consist of one attribute from each side. For example:-

In above diagram, there are three Entities namely Employee, Department and Manager and their corresponding relationships with manager as follows::

1.An employee may belong to multiple departments. So, the relation “belongs_to” means employee belongs to department. Similarly, department may contain many employees so the relationshioes ‘has_many’ mean department contains many employees. Also, managers manage departments and employees respectively. The relationship “manages” stands for department.

2. Employees report to Managers. This situation creates a bi-directional relationship called supervisor/supervisee.

3. Employees receive raises based on performance. Here, raise is considered as an action towards another entity i.e., employee. Therefore, the relationship “receives” means when an employee gets a raise he receives money from his boss.

4. Finally, every employee is given salary once per year. Salary is the monetary value paid to an employee. In order to calculate annual pay, you need to multiply monthly pay by 12. Thus, yearly salary is calculated using below formula::

YearlySalary MonthlyPay * 12

What do you think about the quality of the explanation provided? Why did your professor decide to give this topic?

It’s good but I feel that some information is missing such as who created the model and when it was introduced. Who designed the system and why? What were the objectives behind creating this model? Which problems does this model solve or help to address?

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