Foreign keys establish relationships between tables from "summary" of SQL and Relational Theory by C. Date
It's crucial to understand the role of foreign keys in SQL databases. Foreign keys are used to establish relationships between tables, linking rows in one table to rows in another. This relationship is fundamental to maintaining the integrity and consistency of the data within the database. When a foreign key is defined in a table, it creates a constraint that enforces referential integrity. This means that the values in the foreign key column must correspond to values in the primary key column of another table. This ensures that there are no orphaned rows or inconsistencies in the data. By establishing these relationships between tables, foreign keys enable us to retrieve related data efficiently through JOIN operations. JOINs allow us to combine data from multiple tables based on the relationships defined by foreign keys, providing a comprehensive view of the data. In addition to enforcing referential integrity and enabling JOIN operations, foreign keys also play a crucial role in data modification. When a row with a foreign key is updated or deleted, the database will enforce constraints to maintain the integrity of the relationships between tables.- Foreign keys are a powerful feature of SQL databases that facilitate data consistency, integrity, and efficient data retrieval through the establishment of relationships between tables. Understanding how foreign keys work is essential for designing well-structured and reliable databases.
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