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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?

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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.

  • Hi Laurenz, thanks for the answer. Okay, that clarifies it perfectly. Much appreciated. – Chris Crawshaw Oct 9 at 0:38

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