title: SQL In one list but not another
body: <p>Have three tables Vehicle, VehicleGroup and AssignedVehicleGroup which have the following format:</p>
  
  <p><b>Vehicle</b> - vehicleId, customerId, registration</p>
  
  <p><b>VehicleGroup</b> - groupId, groupName</p>
  
  <p><b>AssignedVehicleGroup</b> - vehicleId, groupId</p>
  
  <p>Vehicles can be placed in more than one group using this schema however I am struggling to write a single query that can find :</p>
  
  <ul>
  <li>All vehicles that are not allocated to any group</li>
  <li>All vehicles that are not in the current group (based on variable passed in)</li>
  </ul>
  
  <p>This query will populate a list that allows user to add vehicle to current group if it is not already in the current group or in any group.</p>