Primary Keys

A primary key is the primary identifier for a table, and is attached to 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.

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.

1. Double-click a table in the diagram to open its property sheet.
2. Click the Columns tab, and select the check box in the P column for one or more columns in the list.
3. [optional] Click the Keys tab and rename the key or select it and click the Properties tool to access its property sheet.
4. Click OK.

• Rebuilding Primary Keys
  Rebuilding primary keys in a physical diagram updates primary keys for tables.