Beat Signer - Department of Computer Science -
[email protected] 25
March 6, 2019
Functional Dependencies
▪ In this example, there are various sets of attributes that
uniquely identify a set of other attributes
▪ teacherID → teacher
▪ teacherID → salary
▪ teacherID → {teacher, salary}
▪ {teacherID, teacher} → {salary}
▪ department → {building, budget}
▪ ...
▪ We say that there is a functional dependency (→)
between these two sets of attributes
▪ a functional dependency should always hold on a relation schema
and not just on a particular relation instance
TeacherDept (teacherID, teacher, salary, department, building, budget)