Many-to-one

Many-to-one ( M:1, also known as a one-to-many relationship) is a type of relationship typically found in database design. It describes a relationship that exists between two entities, where a single instance of one entity can be associated with multiple instances of the other entity. This is the opposite of one-to-one relationships in which each instance of the first entity should only be associated with one instance of the second entity.

For example, a many-to-one relationship can exist between a Company and an EmploymentType table, since a single Company can have multiple types of employees (e.g., Intern, Full-time, Part-time).

Many-to-one relationships are often used in the relational database model as the basis for efficient communication between entities, the most basic form being the join table. In a join table, two tables share a common field, allowing the two tables to be joined or correlated. This is accomplished by creating a new third table which links the entries of the two original tables.

Many-to-one relationships are also commonly found in object-oriented programming. It is a common way of representing relationships between classes, and it is often used in databases to represent the relationships between different entities.

As a result, many-to-one relationships are an important and powerful tool when it comes to database design and building software applications. By establishing and defining a many-to-one relationship, the programmer is able to quickly and easily store and access data, as well as access related data from other databases. This makes many-to-one relationships invaluable for any software development project.