ASA SQL User's Guide
  Monitoring and Improving Performance
    Using keys to improve query performance

Using primary keys to improve query performance

A primary key improves performance on the following statement:

SELECT *
FROM employee
WHERE emp_id = 390

Information on the Plan tab 

The Plan tab in the Results pane contains the following information:

employee <employee>

Whenever the name inside the parentheses on the Plan tab PLAN description is the same as the name of the table, it means that the primary key for the table is used to improve performance.