Restrict user to add "3rd" entry if capacity is 2

Restrict user to add "3rd" entry if capacity is 2https://community.appian.com/discussions/f/user-interface/24140/restrict-user-to-add-3rd-entry-if-capacity-is-2Hi, I have 2 tables pen and animal table , when i am adding the animal i am assigning the pen to the animal and the pen name are coming from pen table, i want to restrict user to add "3rd" animal if i have already set the capacity of pen to 2 animalsen-USTelligent Community 12RE: Restrict user to add "3rd" entry if capacity is 2https://community.appian.com/thread/93065?ContentTypeID=1Thu, 31 Mar 2022 12:23:28 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:a898cec0-ea84-4efb-a038-5df7844d5717Mathieu Drouin<p>You'll have to do an expression rule that queries the database (query entity or record type) and checks the number of animals for a particular pen. You can then use that query in the validations attribute of the Pen name field.</p><div style="clear:both;"></div>