SELECT DISTINCT p.id AS id,
p.precio AS precio,
p.tipo_libro,
p.url_ebook,
p.autor AS autor,
p.activo AS activo
FROM producto AS p JOIN producto_categoria AS pd2
ON( p.id = pd2.producto_id AND pd2.categoria_id = '39' ) WHERE p.activo = 1 AND p.tipo_libro > 0 GROUP BY p.id
