What does referential integrity ensure in a relational database?

Referential integrity is a fundamental principle in relational database design that ensures the accuracy and consistency of data within the relationships among tables. Specifically, it guarantees that every foreign key in a child table corresponds to a valid, existing primary key in a parent table.

This means that if a record in one table references a record in another table, the referenced record must exist. For example, if a customer table includes an order table where each order references the customer who placed it, referential integrity ensures that every order entry points to a valid, existing customer, thereby preventing orphaned records that could lead to inconsistencies and errors in data retrieval and analysis.

This principle is crucial for maintaining the relational structure of the database, allowing for reliable queries and relationships between different data entities. The enforcement of referential integrity helps eliminate issues related to data anomalies and supports accurate data lifecycle management.