This lecture explains how to convert Entity-Relationship (ER) diagrams into relational database models. It covers many-to-many relationships (requiring three tables), many-to-one relationships (requiring two tables), one-to-one relationships (requiring two tables), and weak entity sets (requiring two tables). The lecture emphasizes the importance of primary and foreign keys, composite keys, and participation constraints in creating accurate relational models from ER diagrams. To represent a many-to-many relationship in a relational model, three tables are required. One table represents each entity involved in the relationship, and a third table represents the relationship itself. For example, consider a many-to-many relationship between students and courses. We would have: Student Table: student_number (primary key), student_name Course Table: course_number (primary key), course_name Enrollment Table: student_number (foreign key referencing Student), course_number (foreign key referencing Course) The Enrollment table's attributes are the primary keys of the Student and Course tables, enabling the representation of the many-to-many relationship.