title: Create a Timer which execute a SQL Query for Example after 20 min?
body: <p>in front of a Room i have a Panel. That Panel is displaying the occupancy time, for example 14:00 - 15:30. If someone want to use that Room for that time he has to push a CHECK_IN Button on the Panel. So the system knows there is someone in the Room. Now i want that if nobody use that Button after 20 min from 14:00, the occupancy time should be canceled.</p>
  
  <p>i have already written the Query for the cancel.
  But i need something similar to a Timer, which execute the Query after 20 min. 
  How can i do that?</p>
  
  <p>Thanks in advance</p>