What is the difference between er diagram and class diagram

It is a method by which the conceptual model of a system is produced. The diagrams produced by this method are called entity-relationship diagrams. These diagrams do not show one single entity; they show a set of entities or a set of relationships. The sets of entities are represented by rectangles, and diamonds represent relationship sets in an ERD. A line connects when a relationship entity is participated in by an entity set. Ovals are used to represent attributes.

The ERDs are used to represent the information or type of information required to be stored in a database. They are used as a requirement for analysis. Summary: The class diagrams are used to represent the main object or building block of the system. They are used to show the relationship of one class with another and also represent the attributes of the system. However, an ERD is more of a database in the form of tables. Main building blocks of ER diagrams are entities, relationships and attributes.

An entity represents a thing that can exist independently and that can be defined uniquely. Most often, an entity represents a real world object such as a car or an employee. Entities can be though of as nouns that come up during the description of the problem to be solved. Relationship shows how entities are connected. They are like verbs found in the description of the problem to be solved. Properties of both entities and attributes are called attributes.

A class diagram more correctly known as a UML class diagram is a design diagram that represents the static structure and the behavior of a proposed system, defined using UML Unified Modeling Language. Thus, these are the properties of the class.

The third or the last row, on the other hand, has the methods. They represent the operations the class can use. Furthermore, these methods help to understand how a class interacts with data. Interactions represent the relationship between the classes. Some common interaction types are inheritance, bidirectional association, and unidirectional association. Inheritance allows the subclasses to use the attributes and methods of the superclass. In contrast, the bidirectional association is the default relationship between the two classes while unidirectional association represents navigation only to a single class.

An entity is a real-world object. ER diagram represents the entities and their associations. For example, a hospital database has separate tables for patients, doctors, and medical reports.

Each of them is an entity. In the ER diagram, a rectangle signifies an entity. In this paper we look specifically at concepts which can cause problems for the novice database designer due to this conceptual mismatch.

Firstly, transferring the mapping of a weak entity from an Entity Relationship model to UML and secondly the representation of many-to-many relationships. We also look at the mixture of notations which students mistakenly use when modelling. This is often the result of different notations being used on different courses throughout their degree.