January 2019
Beginner
556 pages
14h 19m
English
Content preview from Learning PostgreSQL 11 - Third Edition
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Referential integrity constraints
Relations are associated with each other via common attributes. Referential integrity constraints govern the association between two relations and ensure data consistency between tuples. If a tuple in one relation references a tuple in another relation, then the referenced tuple must exist. In the customer service example, if a service is assigned to a customer, then the service and the customer must exist, as shown in the following example:
For instance, in the customer_service relation, we cannot have a tuple with values (5, 1,01-01-2014, NULL), because we do not have a customer with customer_id equal to ...
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