Referential integrity is a data integrity rule in relational databases. It ensures accuracy and consistency of data in one or more related tables. This rule states that every value in a given column must have a matching foreign key (or reference key) value in a related table. This helps to maintain a link between related data, and it confirms that any data being changed or deleted in one table is also changed or deleted in the related database.
Referential integrity helps to ensure the accuracy of data across multiple tables and helps prevent data “orphaning,” where values exist without relation. If a referential constraint is violated, a database can reject the changes with an error message.
For example, in a database of customers, a customer may have an order; the customer in the customer table would have a customer_ID field. The order table would include customer_ID as a foreign key, which allows that table to reference the customer’s data. If an order is deleted from the order table, the customer_ID in the customer table will be left unchanged; otherwise, it would violate the referential integrity constraint.
Referential integrity rules are important for protecting the accuracy and consistency of data in a database. They ensure that data that is related is updated or deleted simultaneously, and that any non-related data is erased in one table, leaving the other table unaffected. These rules help maintain consistent data across multiple tables, which is essential for accurate data-driven decision making.
