Uniqueness Constraints
Explore how uniqueness constraints enforce data integrity in front-end web applications. Understand key concepts like unique attributes, composite keys, and standard identifiers as primary keys. Learn practical ways to implement these constraints in JavaScript to build reliable and well-validated applications.
We'll cover the following...
A uniqueness constraint (or key constraint) requires that a property’s value—or the value list of a list of properties in the case of a composite key constraint—is unique among all instances of the given object type.
Uniqueness constraints in UML
For instance, in a UML class diagram with the object type Book, we can define the isbn attribute to be unique (or a key) by appending the user-defined property modifier keyword key in curly braces to the attribute’s definition in the Book class rectangle. This is shown in the following diagram:
In an SQL table creation ...