Set union, returns rows in the left relations and each right relation. Accepts multiple tables/queries as parameters.
Same kind of thing as clojure.set/union.
Examples
(def Mary[[:from:Customer][:where[= :firstname"Mary"]]])(def John[[:from:Customer][:where[= :firstname"John"]]])(def JohnAndMary[[:fromJohn][:unionMary]]);; union doesn't need a left side;; the below would also work.[[:unionJohnMary]]