Description: A foreign key is a field in a table that uniquely identifies a row in another table, thereby establishing a relationship between both. This concept is fundamental in the design of relational databases, where the aim is to maintain referential integrity. The foreign key allows one table to reference the primary key of another, ensuring that the data is coherently related. For example, in a library database, a ‘Books’ table might have a foreign key pointing to the ‘Authors’ table, linking each book to its respective author. Foreign keys are essential to avoid data duplication and to facilitate complex queries involving multiple tables. Additionally, they allow for the implementation of constraints that ensure that data cannot be inserted into a table without a valid correspondence in the referenced table, contributing to the quality and consistency of the stored information.
