Lecture 5 - Entity Relationship Diagram
ERD is a way of representing database relations in a graphical form. As you know that the entities are represented using rectangle and attributes using ovals. Let’s revisit the relationship of a teacher and student. As you can see that one teacher teaches many students. First Relation Second Relation Similarly, many subjects are studied by many students. Merge Relations Now! You must be thinking what is the relationship of teacher and subject? Probably your answer is many-to-many . . . I would rather disagree with your point of view; the reason will be discussed with you when we would implement this ERD in a DBMS. The completed ERD would be Finalized Relations That was simple ERD; it cannot be implemented in any DBMS. What else is required? What is missing? Do you remember the term ‘attribute’? Yes the answer is ‘attributes’ which are not defined. Let’s define some attributes ...
