How do you handle many-to-many relationships in RDBMS?

In RDBMS, many-to-many relationships are handled by creating a junction table, also known as a bridge table.

In a relational database management system (RDBMS), relationships between tables are crucial for organising and accessing data efficiently. One of the more complex relationships is the many-to-many relationship. This occurs when multiple records in a table are associated with multiple records in another table. For example, in a school database, a student can be enrolled in multiple courses, and a course can have multiple students. This is a many-to-many relationship.

To handle this, we use a junction table, also known as a bridge table, link table, or associative table. This is a table that serves as a bridge between the two tables that have the many-to-many relationship. The junction table contains foreign keys that reference the primary keys of the two tables it connects.

In our school example, the junction table might be called 'Enrollments'. It would have a 'StudentID' column and a 'CourseID' column. Each row in the 'Enrollments' table represents a unique combination of a student and a course, i.e., an enrollment. The 'StudentID' and 'CourseID' are foreign keys referencing the primary keys in the 'Students' and 'Courses' tables, respectively.

This structure allows us to efficiently query the database for all the courses a particular student is enrolled in, or all the students enrolled in a particular course. It also allows us to add or remove enrollments without affecting the 'Students' or 'Courses' tables.

It's important to note that the junction table can also contain additional information related to the relationship. For example, the 'Enrollments' table might also have a 'DateEnrolled' column to record when each student enrolled in each course.

In summary, handling many-to-many relationships in RDBMS involves creating a junction table that bridges the two tables with the many-to-many relationship. This table contains foreign keys referencing the primary keys of the two tables it connects, and can also contain additional information related to the relationship.