What is a “part-key”?

Question

I'm a beginner and student with regards to database design. The tutor recently discussed “part-keys”. I am struggling to find any information on what a part-key is, and I suspect it probably goes by another name.

The example we were given in class was this:

ACTIVITY(Activity(PK), Fee)
STUDENT_ACTIVITY(StudentID(PK), Activity(PK))

Is the table showing part-key dependency?

Yes. Since the second determinant (Activity) is part of the primary key (StudentID, Activity).

Is anyone able to give me any further information?

Answer 1

This example does not contain a partial dependency to me.

A partial dependency would be if a table column functionally depends on part of the table's primary key, like in this denormalized table:

CREATE TABLE student_activity (
   studentid bigint NOT NULL,
   activity character varying(30) NOT NULL,
   fee numeric(10,2) NOT NULL,
   PRIMARY KEY (studentid, activity)
);

where fee depends on activity.

The solution would be to split this table in two parts like in your question.