What does the term 'Refer' in Referential Integrity mean?

The term 'Refer' in Referential Integrity primarily relates to the concept of linking data between tables. Referential Integrity is a fundamental principle in relational database design that ensures that relationships between tables remain consistent and valid. This means that for any foreign key in one table, there should be a corresponding primary key in another table.

When a foreign key references a primary key from another table, it establishes a connection or link between the records in those tables. If a record in one table points to a non-existent record in another table, it can lead to data integrity issues. Thus, the key aspect of Referential Integrity is about maintaining valid links between tables, ensuring that all references are legit and that the data reflects accurate relationships, crucial for maintaining the integrity and usability of the database.

In the context of the other choices, while defining relationships or deleting related records are actions that may relate to maintaining integrity, they do not capture the essence of the term 'Refer' as it specifically pertains to the practices of maintaining valid links between tables.