title: Sql joins Displaying only available times
body: <p>What I'm trying to do is the following:-</p>
  
  <p>Query my database to show only the time-slots which haven't been used and populate it to a drop down box. (I know how to populate it to the drop down box.)</p>
  
  <p>This is what I have:-
  (Tables)</p>
  
  <pre><code>     Appointment:-             Availability:-
       AppointmentTime           AvailabilityTime
       AppointmentDate           EmployeeId
       ClientID
       EmployeeId
  </code></pre>
  
  <p>From researching around I'm pretty certain I need to have a join command in my SQL statement. </p>
  
  <p>To me the logical way of doing this is that in order to achieve what I want I need to check the AvailabilityTime and employee ID against that in the appointments table and if there isn't a match that should mean that chosen appointment time is free so this gives grounds to display all available free slots.</p>
  
  <p>The problem is I am not quite sure how to go about doing this SQL wise, any suggestions would be greatly appreciated!</p>