Utiliser SELECT UNION et renvoyer la sortie de deux colonnes d'une table

Une autre façon (sans CASE expression):

SELECT 
  ( SELECT COUNT(*)
    FROM tblActor 
    WHERE ActorGender = 'm' 
  ) AS MaleActors
, ( SELECT COUNT(*)
    FROM tblActor 
    WHERE ActorGender = 'f' 
  ) AS FemaleActors
FROM 
    dual ;

et plus de solutions avec CROSS rejoindre :

SELECT m.MaleActors, f.FemaleActors
FROM 
  ( SELECT COUNT(*) AS MaleActors
    FROM tblActor 
    WHERE ActorGender = 'm' 
  ) m
  CROSS JOIN
  ( SELECT COUNT(*) AS FemaleActors
    FROM tblActor 
    WHERE ActorGender = 'f' 
  ) f  ;