How to clear all plans from a single database?
DBCC FLUSHPROCINDB (&lt;db_id&gt;)


This command allows you to specify a particular database id, and then clears all plans from that particular database. Check more information here.



DBCC FREEPROCCACHE


This command removes all cached plans from memory


  It is, of course, recommended that you don’t use these commands on
  your production servers, as it could impact the performance of your
  running applications. Usually, you want to keep plans in cache.