What are associative entities?
In the Entity-Relationship model, where data is abstract and conceptually represented in software engineering, associative entities are one part of the model. Relational models are often created to represent data in a database or system where they are used to organize data into a comprehensible and readable scheme. Entities in a relational model could represent anything, including people, places, objects, events or concepts. Associative entities are a connection that describes the relationship between two different entities. These entities can have many associative entities, which may have many relationships between people, which means that one of the associative entities can have more relationships and connections with a parent or child entity.
They are considered an entity because they have attributes and are considered a relationship because they combine entities together. Very often these types of entities have many links because they are attributed but can have independent importance from other entities. For AssociatThe iva entity is also a good practice in a relational model that has at least one attribute that is distinguishable from the entity of the identifier. Associative entities may also be participants in relations separated from relationships with associated entities.
The primary keys should also be part of associative entities, as they are identifiers adjacent to certain tables in the relational model. Although tables may contain only one, the primary keys are a combination of columns that uniquely specify rows. There is a difference between unique keys and primary keys, in the fact that the primary keys can force the "not zero" restriction in the table or entity. Another aspect that distinguishes the primary keys from the unique key. Primary indices are created to manage primary keys and for easy use and recovery using a database manager.
Associative entities are contained and used in tablesConnection - tables in a relational model that contains common fields from two or more other tables. Junction tables are used because they can deal with relationships with many or people in a database. One example of a database that uses the associative entity using a junction with the intersection is the registration of students in the course. In this case, the table with students data is indirectly associated with a table with courses data via an intermediate table that contains data associated with student data and course from the interconnection tables.