Many-to-Many is a term used to describe a type of relationship between two entities in a database. An entity is a person, place, thing, or concept about which data is stored. This type of relationship is required when an individual record in one entity can be related to multiple records in the second, and vice versa.
For example, a many-to-many relationship between the entities customers and products would mean that each customer can order multiple products and each product can be ordered by multiple customers. Additionally, customers and products can share attributes such as price, availability, and delivery cost.
A many-to-many relationship is used in databases to link two entities in order to simplify data analysis. Many-to-many relationships are recursive, meaning that the same type of relationship can occur between two different entities multiple times, and a single record can appear in both entities at the same time.
Though, the relationship between two entities will depend on the application – many different techniques can be used to model a many-to-many relationship in a database. One popular approach is to create a third entity, or junction table, that serves as a link between the two original entities. This junction table holds the information about the relationship between the two entities and provides the necessary data to create proper queries.
In summary, many-to-many relationships are used by database applications to create relationships between two entities, allowing multiple interactions between the entities. This type of relationship allows for more complex data analysis and helps to simplify the process of maintaining large databases.
