UML Modeling Techniques > Data modeling > Data modeling overview > Displaying prime and foreign keys
Displaying prime and foreign keys
A prime key is the unique identifier for a table that can consist of one or more columns. On a diagram, the name of a prime key is underlined.
To define a column as a prime key:
1. For each Column that is used to define the prime key:
a. Select the column.
You can select the column either in the Table Relationships Diagram or in the Dictionary window.
b. In the Property pages, display the Options tab.
c. Clear the Can be Null check box, and then select the Prime check box.
When you display the Table on a Table Relationships Diagram, the columns that make up the prime key are underlined.
Foreign keys
A table can have a number of relationships with other tables. The prime key in the master table corresponds to a foreign key in the detail table.
Foreign keys are automatically propagated from prime keys in master tables through 1:many relationships.
On the diagram a foreign key is shown by an asterisk (*), in the Options properties tab a message is displayed to say whether a column is a foreign key or not.