Viiteväärtustega

Viiteväärtustega, often translated as "referential values" or "referential integrity," is a fundamental concept in relational database management systems. It ensures the accuracy and consistency of data by establishing relationships between tables. Specifically, it refers to the rules that govern how changes in one table affect corresponding entries in another.

The core principle of viiteväärtustega is that foreign keys in one table must always refer to valid primary keys in another table. A primary key is a unique identifier for each row in a table, while a foreign key is a column or set of columns in one table that refers to the primary key in another. This linkage creates a relationship, such as a customer ID in an orders table referencing the primary key of a customers table.

When viiteväärtustega is implemented, the database system enforces certain actions to maintain these relationships. For example, if a record is deleted from the primary table, the database can be configured to either delete the corresponding records in the referencing table (cascade delete), set the foreign key values to null, or prevent the deletion altogether. Similarly, updates to primary keys can be cascaded to update foreign keys.

The benefits of viiteväärtustega include preventing orphaned records (records in a child table that do not have a corresponding parent record), reducing data redundancy, and improving the overall quality and reliability of the database. It is a crucial component for maintaining data integrity in complex database designs.