Adding primary keys


A primary key is the column or minimal combination of columns which uniquely identifies each row in a table.

Primary keys can be created in two ways: by using the toolbar or by directly entering the information in the model’s properties window.
Example: employee number, company code, department number.
  1. Select the key tool in the Open ModelSphere toolbar.

  2. Choose the column that you want to designate as a key. The column will be underlined to denote that it is a primary key column. (If you pick the wrong column, use the Key tool to remove the underline)


  3. Remember that primary keys can be composed of multiple columns. Simply select the additional columns that will be part of the key.

  4. Add the primary keys to your diagram as shown in the following data model.



In Open ModelSphere, primary keys are underlined to distinguish them from other columns. In the example above, all four tables have a primary key composed of a single column. For example, in the Project table, Team project’s number is used to identify each project, and Employee number uniquely identifies each employee in the Employees table.