Foreign keys (DormitoryID, RoomID, StudentID) establish relationships between entities by referring to primary keys from their respective tables.
Correct. A foreign key is a column or a set of columns in one table that refers to the primary key in another table. It establishes a relationship between entities by creating a link between the two tables. In this example, the foreign keys (DormitoryID, RoomID, StudentID) refer to the primary keys of the respective tables, creating relationships between the dormitory, room, and student entities.
Foreign keys are used in relational databases to establish relationships between tables. In this case, the foreign keys (DormitoryID, RoomID, StudentID) are referring to the primary keys of their respective tables to establish relationships.
Here is a step-by-step explanation of how these foreign keys establish relationships between entities:
1. Identify the tables: We have three tables involved in this relationship – Dormitory, Room, and Student.
2. Primary keys: Each of these tables should have a primary key. Let's assume DormitoryID is the primary key for the Dormitory table, RoomID is the primary key for the Room table, and StudentID is the primary key for the Student table.
3. Foreign keys: In the table where the relationship needs to be established (let's say the Room table), we include foreign keys that reference the primary keys from the related tables. In this case, DormitoryID, RoomID, and StudentID are the foreign keys in the Room table.
4. Relationship type: Based on the purpose of the relationship, we can determine the type of relationship. It could be a one-to-many, many-to-many, or one-to-one relationship. For example, if DormitoryID and RoomID together form a composite foreign key in the Room table, it would indicate a one-to-many relationship between the Dormitory and Room tables, where one dormitory can have multiple rooms.
5. Referential integrity: To maintain data integrity, referential integrity constraints need to be enforced. This ensures that the foreign key values in the referencing table (Room table) match the primary key values in the referenced table (Dormitory and Student tables).
In summary, the foreign keys (DormitoryID, RoomID, StudentID) establish relationships between entities by referring to the primary keys from their respective tables. This allows for linking related data across multiple tables and enforcing data integrity.