DBMS Notes

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.
  • Designer design the ER model and then programmer develop 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 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 next lecture we will discuss about all components one by one

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