Partial dependency

Refers to the dependence of non-prime attributes on only a part (a proper subset) of the composite primary key, rather than on the entire key.

Example §

StudentCourses
--------------
StudentID  |  CourseID  |  StudentName  |  CourseName
----------------------------------------------------
101       |  C001      |  John         |  Math
101       |  C002      |  John         |  Science
102       |  C001      |  Emily        |  Math

• Candidate key - (StudentID, CourseID)
• StudentName is dependent only on StudentID (similarly CourseName) - partial dependecy
• The partial dependency can be eliminated by separating the table into 2,

StudentID  |  StudentName
-------------------------
101       |  John
102       |  Emily

CourseID  |  CourseName
----------------------
C001      |  Math
C002      |  Science

StudentCourses
--------------
StudentID  |  CourseID
---------------------
101       |  C001
101       |  C002
102       |  C001