Dependency theory is a subfield of
database theory
Database theory encapsulates a broad range of topics related to the study and research of the theoretical realm of databases and database management systems.
Theoretical aspects of data management include, among other areas, the foundations of q ...
which studies implication and optimization problems related to logical constraints, commonly called dependencies, on databases.
The best known class of such dependencies are
functional dependencies, which form the foundation of
keys on database relations. Another important class of dependencies are the
multivalued dependencies. A key algorithm in dependency theory is the
chase
Chase or CHASE may refer to:
Businesses
* Chase Bank, a national bank based in New York City, New York
* Chase Aircraft (1943–1954), a defunct American aircraft manufacturing company
* Chase Coaches, a defunct bus operator in England
* Chase Co ...
, and much of the theory is devoted to its study.
Dependencies
*
functional dependency
In relational database theory, a functional dependency is a constraint between two sets of attributes in a relation from a database. In other words, a functional dependency is a constraint between two attributes in a relation.
Given a relation ' ...
*
join dependency In database theory, a join dependency is a constraint on the set of legal relations over a database scheme. A table T is subject to a join dependency if T can always be recreated by joining multiple tables each having a subset of the attributes of ...
*
multivalued dependency In database theory, a multivalued dependency is a full constraint between two sets of attributes in a relation.
In contrast to the functional dependency, the multivalued dependency requires that certain tuples be present in a relation. Therefore, ...
*
tuple-generating dependency In relational database theory, a tuple-generating dependency (TGD) is a certain kind of constraint on a relational database. It is a subclass of the class of embedded dependencies (EDs).
An algorithm known as the chase takes as input an instance ...
*
equality-generating dependency
*
embedded dependency
*
inclusion dependency
*
full typed dependency
{{database-stub
Database theory
Database constraints