Kardinaliteitsbeperking

Kardinaliteitsbeperking is a concept used in database design and modeling, particularly in the context of relationships between entities. It specifies the number of instances of one entity that can be associated with an instance of another entity. This helps to enforce data integrity and accurately represent real-world constraints. There are generally four types of cardinality constraints: one-to-one (1:1), one-to-many (1:N), many-to-one (N:1), and many-to-many (N:M).

A one-to-one relationship means that a single instance of entity A can be related to at most one instance of entity B, and vice versa. For example, a person might have one passport, and a passport belongs to only one person.

A one-to-many relationship indicates that one instance of entity A can be related to many instances of entity B, but each instance of entity B can only be related to one instance of entity A. An example is a customer who can place many orders, but each order is placed by only one customer.

A many-to-one relationship is the inverse of one-to-many, where many instances of entity A can be related to one instance of entity B. This is often seen in conjunction with one-to-many relationships.

A many-to-many relationship signifies that one instance of entity A can be related to many instances of entity B, and vice versa. For instance, a student can enroll in many courses, and a course can have many students. In database implementation, many-to-many relationships are typically resolved using an intermediate or junction table. Understanding and applying cardinality constraints correctly is crucial for building robust and efficient databases.