Data Modeling › Data Model › Entering Relation Statements

Entering Relation Statements

Working top down, define the most basic entities in your data model: COURSE and RACE.

To do this you will use three different CA 2E relations:

Known by

Declares a field that is part of the primary key that uniquely identifies a file

Has

Declares a non-key field (attribute) on a file

Owned by

Specifies a relationship between two files; the primary key of the owning file becomes part of the primary key of the owned file

For example, in the tutorial model, RACE is Owned by COURSE. COURSE is uniquely identified by a Course code. Since RACE is Owned by COURSE, each RACE is uniquely identified by a combination of the COURSE at which it is run, a date, and a time. As a result, the primary key for RACE consists of Course code, Race Date, and Race Time.

Type in relations as shown and use the Tab key or the Field Exit key to advance to the next field or line.

Note: Following are two shortcuts for entering relations.

• You can use the DUP key (indicated by the string of *‘s in the above panel) to reduce the amount of typing. When the cursor is in a field and you press the DUP key, values from the previous line will be duplicated on the line below when you press Enter.
• You only need to type the first letter of a relation; for example, you can type K or O in place of Known by or Owned by, respectively.

Press Enter after entering all the relations shown.