Expressing A Composite Key in a Data Dictionary

Question

I am looking for an example of expressing a "Composite Keys" in a data dictionary.

I am using an MSO Access application with a Lecturer Table and Subjects Table where I have taken the Primary Keys from their tables to create a table called Timetable.

From the information building the database file I must create a Data Dictionary but was caught off guard when I had to question myself in explaining the referencing of these two fields that create them as a Composite Key.

My "Data Dictionary" is comprised of a Field Name, Data Type with Field Size, Constraints, References and Field Description.

I have found it difficult to find any subjects on this matter which is directed by how a Composite Key in a Data Dictionary may be expressed and hope I may get some ideas here.

Answer 1

Notation for composite keys typically takes the form of:

(key1, key2)

This can be seen in the T-SQL language, per:

CREATE TABLE dbo.lecturers
(
    lecturer_name varchar(30) NOT NULL
        PRIMARY KEY
);

CREATE TABLE dbo.subjects
(
    subject_name varchar(30) NOT NULL
        PRIMARY KEY
);

CREATE TABLE dbo.timetable
(
      lecturer_name varchar(30) NOT NULL
        FOREIGN KEY
        REFERENCES dbo.lecturers(lecturer_name)
    , subject_name varchar(30) NOT NULL
        FOREIGN KEY
        REFERENCES dbo.subjects(subject_name)
    , PRIMARY KEY (lecturer_name, subject_name)
);

In the above example, the composite primary key for dbo.timetable is expressed as (lecturer_name, subject_name).