Computes the set-theoretic union of two collections. The union of two sets is all items that appear in either of the sets. If an item appears X times in one set, and Y times in the other set, the union contains the item Maximum(X,Y) times. The source collections are not changed. A new collection is created with the union of the collections; the order of the items in this collection is undefined.

Computes the set-theoretic union of two collections. The union of two sets is all items that appear in either of the sets. If an item appears X times in one set, and Y times in the other set, the union contains the item Maximum(X,Y) times. The source collections are not changed. A new collection is created with the union of the collections; the order of the items in this collection is undefined.