Aggregate functions such as sum, max etc. are readily available in Datomic's Datalog implementation. They are written in the :find clause in your query:
[:find (max ?date)
:where
...]An aggregate function collects values from multiple datoms and returns
min, max, sum, avg, etc.(min n ?d) (max n ?d) (sample n ?e) etc. where n is an integer specifying the size of the collection.Given a collection of actors and (the now familiar) ratings data. Find the average rating for each actor. The query should return the actor name and the avg rating.