select b.name as "Band Name",s."Number of songs" from bands as b inner join(select a.band_id as "id",count(s.length) as "Number of songs" from albums as a inner join songs as s on a.id=s.album_id group by a.band_id) as s on b.id=s.id;
Please try with the query given inside the inner join first and then do the rest for easy understanding from beginner point of view
select b.name as "Band Name",s."Number of songs" from bands as b inner join(select a.band_id as "id",count(s.length) as "Number of songs" from albums as a inner join songs as s on a.id=s.album_id group by a.band_id) as s on b.id=s.id;
Please try with the query given inside the inner join first and then do the rest for easy understanding from beginner point of view