SQL Foreign Key

Foreign keys are a fundamental aspect of relational database design. They establish relationships between tables by referencing primary keys in other tables. This connection is vital for maintaining data integrity. Imagine a database for an online store. You have a table for products and a table for orders. A foreign key in the orders table would reference the primary key in the products table, ensuring that every order refers to a valid product. Without a foreign key, an order could be placed for a product that no longer exists, leading to inconsistencies and errors. Foreign keys prevent such issues by enforcing a link between tables. They act as a safeguard, ensuring that data in related tables remains consistent. This constraint is crucial for maintaining data accuracy and preventing data anomalies. For example, if a product is deleted from the products table, any orders referencing that product will be flagged as invalid or potentially deleted, depending on the specific constraint setup.