Chapter 3 Building Physical Diagrams

Designating a primary key

A primary key is the primary identifier for a table. A primary key is made up of one or more columns whose values uniquely identify every row in the table.

Every table must have a primary key, composed of one or more of its columns.

Example

Employee number is the primary key for the table Employee. This means that each employee must have one unique employee number.

You can define one or more columns as the primary key of a table from the list of columns.

To designate a primary key:

1. Double-click a table in the diagram to display the table property sheet.
2. Click the Columns tab.
   
   The Columns page appears. It lists the columns associated with the table.
3. Select one or more columns in the list.
4. Select the check box in the P column.
5. Click OK.

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