-- Database schema
| mountain : id [ INT ] primary_key , name [ TEXT ] , Height [ INT ] , Prominence [ INT ] , Range [ TEXT ] , Country [ TEXT ] | camera_lens : id [ INT ] primary_key , brand [ TEXT ] , name [ TEXT ] , focal_length_mm [ INT ] , max_aperture [ INT ] | photos : id [ INT ] primary_key , camera_lens_id [ INT ] photos.camera_lens_id = camera_lens.id , mountain_id [ INT ] photos.mountain_id = mountain.id , color [ TEXT ] , name [ TEXT ] |
-- -- Show the name and prominence of the mountains whose picture is not taken by a lens of brand 'Sigma'.

SELECT name ,  prominence FROM mountain EXCEPT SELECT T1.name ,  T1.prominence FROM mountain AS T1 JOIN photos AS T2 ON T1.id  =  T2.mountain_id JOIN camera_lens AS T3 ON T2.camera_lens_id  =  T3.id WHERE T3.brand  =  'Sigma';