ER Model And Its Symbols

  • ER (Entity Relationship) diagram is a graphical representation of the logical structure of the database.
  • It displays all the constraints and relationships that exist among the different components.
  • The designer designs the ER model, and then the programmer develops the entity accordingly.

Must Learn Entity vs Entity Set before to start the topic,

Entity Vs. Entity Set

Consider the following Student table

This complete table is a “Student Entity Set,” and each row represents an “entity.”  So, We can also say there are four entities of the Student entity set. Or we can say there are four instances of “student entity set.”

The above student entity table contains the following ER Diagram

Symbols for ER diagram

 ER diagram contains several components, and each component is represented using a specific symbol.

ER diagram symbols are given below.

 

In the next lecture we will discuss all components one by one.