Execute Insert_all from a select

Questions & Help Questions
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1

I need insert some information of a table in another table.
Is possible to do something like this code (that doesn’ t work) to execute only one query and not 2 separately?
Thanks

followers = from u in User,
            select: %{user_id: u.id, topic_id: ^topic.id},
            inner_join: a in Activity, on: [user_id: u.id],
            where: a.contest_id == ^topic.contest_id
              and a.type == 1
          Repo.insert_all(TopicUser, followers)