Chapter 6, Problem 4PE

Program Plan Intro

Entity-Relationship diagram:

• Entity-Relationship (ER) diagram is the method to represent the relational database using graphical form.
• This graphical representation shows only primary elements such as records, types, attributes, relationships between entities, and so on.
• The graphical representation of the ER diagram clearly describes the relationship among entities.
• In the diagram, every connector is labeled.
  • On one side it is represented by the value 1, and on the other side it is labeled with the value “M”. This labeling is referred to as “cardinality constraint” of the relationship.

Data redundancy:

Database is a group of interrelated and organized data which helps to access, manage, and update the data easily.

• Database should be designed carefully by avoiding inconsistent data, redundant data, and misuse of the data.
• If same data occurs more than once, then it is called data redundancy.
• For example, maintaining two same details in two different tables increases the overall database size and both needs to be updated unnecessarily. Otherwise, it may cause error when retrieving the data.
• Hence, redundant data should be avoided when designing database.