SELECT idCategoria, NombreCategoria, XMLQuery(
'for $x in collection("CatalogoCD")/catalogo/cd
where count($x/artistas/artista) > 1
return 
  <cd id = "{$x/@id}">
    {$x/artistas/artista}
  </cd>'
PASSING CatalogoCD RETURNING CONTENT
) AS Mas1Autor
FROM Categorias
WHERE NombreCategoria = "Discos más Populares"