ER Diagram Examples for School Database

Practical ER Diagrams

School ER Diagram

Entities: Student, Class, Teacher, Subject.

• A Class has many Students (1:N).
• A Teacher teaches many Subjects (1:N).
• A Student studies many Subjects (M:N).

Library ER Diagram

Entities: Member, Book, Issue.

• A Member borrows many Books (M:N, resolved by Issue table).
• Issue stores member_id, book_id, issue_date, return_date.

Converting M:N

A many-to-many relationship is converted into a junction table with two foreign keys. Example: student_subject(roll_no, subject_id).

Summary

• Identify entities, then their relationships and cardinality.
• M:N relationships become junction tables with two foreign keys.

Practical ER Diagrams

School ER Diagram

Entities: Student, Class, Teacher, Subject।

• एक Class में कई Students (1:N)।
• एक Teacher कई Subjects पढ़ाता है (1:N)।
• एक Student कई Subjects पढ़ता है (M:N)।

Library ER Diagram

Entities: Member, Book, Issue।

• एक Member कई Books borrow करता है (M:N, Issue table से resolve)।
• Issue में member_id, book_id, issue_date, return_date।

M:N को Convert करना

Many-to-many relationship एक junction table में बदलती है जिसमें दो foreign keys होती हैं। Example: student_subject(roll_no, subject_id)।

सारांश

• Entities पहचानें, फिर उनके relationships और cardinality।
• M:N relationships दो foreign keys वाली junction tables बनती हैं।