select sum(ABS(now()::date - prog.signed_in_at)) from
(
select distinct signed_in_at from programmers
 join projects_programmers pp ON programmers.id = pp.programmer_id
 join projects p ON p.id = pp.project_id
 join languages l ON l.id = p.language_id
 where l.label = 'ruby'
) as prog;


select projects.name, count(p.id) from projects
join projects_programmers pp ON projects.id = pp.project_id
join programmers p ON p.id = pp.programmer_id
group by projects.name


select projects.name, sum(abs(pp.joined_at - now()::date)) from projects
join projects_programmers pp ON projects.id = pp.project_id
join programmers p ON p.id = pp.programmer_id
group by projects.name




select sub.name from
(select p.name, count(p_p) from projects_programmers p_p
 join projects p on p.id = p_p.project_id
 group by p.name order by count desc, p.name limit 1
) as sub;



select sub.name from
(select p.name, count(p_p) from projects_programmers p_p
 join projects p on p.id = p_p.project_id
 group by p.name order by count desc
) as sub
where sub.count = (select count(p_p) from projects_programmers p_p
    join projects p on p.id = p_p.project_id
    group by p.name order by count desc, p.name limit 1);