title: How do I validate two fields for uniqueness
body: <p>I need to validate the uniqueness of two fields in an object (row) before I add them.  Employee_id and area_id are the two fields in my emp_area table.  There can be multiple records with the same employee_id and multiple records with the same area_id, but no two records can have the same employee_id and the same area_id.  This is sort of like two fields making up a primary-key or unique-key.</p>
  
  <p>How can I do this.  </p>
  
  <p>Thanks</p>