Adding unique keys


It is sometimes possible to identify an entity by keys other than the primary key. These are (combinations of) attributes that have key characteristics (unique and not null); they are called unique keys.

Unique keys are preceded by a sequential number enclosed in brackets: <1> for the first unique key, <2> for the second, etc.

To create an alternate key:
  1. Look for the Key tool and click the arrow next to the key (a display of keys numbered 1 to 5 will appear).
  2. Choose one of those numbered keys.
  3. Click the attribute(s) that will become the unique key.