+Referential integrity is a fundamental rule in [Relational Database](/wiki/relational_database) systems, ensuring that relationships between tables remain valid and consistent. It dictates that a [Foreign Key](/wiki/foreign_key) in one table must always refer to an existing, valid record in another, or be explicitly null, thus preserving [Data Integrity](/wiki/data_integrity) and preventing orphaned data.
+## See also
+- [Primary Key](/wiki/primary_key)
+- [Database Normalization](/wiki/database_normalization)
+- [Database Schema](/wiki/database_schema)