title: Select exactly one row for each employee using unordered field as criteria
body: <p>I have a data set that looks like the following.</p>
  
  <pre><code>EMPLID  PHONE_TYPE  PHONE
  ------  ----------  --------
  100     HOME        111-1111
  100     WORK        222-2222
  101     HOME        333-3333
  102     WORK        444-4444
  103     OTHER       555-5555
  </code></pre>
  
  <p>I want to select exactly one row for each employee using the PHONE_TYPE field to establish preferences.  I want the HOME phone number if the employee has one as is the case for employee 100 and 101.  If the HOME number is not present, I want the WORK number (employee 102), and as a last resort I'll take the OTHER number as with employee 103.  In reality my table has about a dozen values for the PHONE_TYPE field, so I need to be able to extend any solution to include more than just the three values I've shown in the example.  Any thoughts?  Thanks.</p>