Referential Integrity

Referential Integrity in E/R Diagrams

We can extend the arrow notation in E/R diagrams to show whether a relationship is expected to support referential integrity in one or more directions. Suppose R is a relationship from

From E/R Diagrams to Relational Designs

We now consider the process by which a new database, such as our movie database, is created. We start with a design phase, in which we address and answer questions about what

Referential Integrity Constraints

A common kind of constraint, called "referential integrity" in The Modeling of Constraints, declares that a value appearing in one context also appears in another, related context. We saw referential integrity as a matter of relationships "making sense". That is, if an object or

Additional Constraint Examples

The same constraint notation permits us to express far more than referential integrity. For instance, we can express any functional dependency as an algebraic constraint, although the notation is more awkward than the FD notation introduced in Functional Dependencies.

Maintaining Referential Integrity

We have studied how to declare a foreign key, and we learned that this declaration implies that any set of values for the attributes of the foreign key, none of which are NULL, must also appear in the corresponding attribute(s) of the referenced relation. But how is this constraint

Constraints on Attributes and Tuples

We have seen key constraints, which compel certain attributes to have distinct values among all the tuples of a relation, and we have seen foreign-key constraints, which enforce referential integrity between attributes of two relations. Now, we shall see a third important kind of

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