续集：如何使用组和计数

简单地说，我如何使用Sequel进行此查询？

select a.id, count(t.id) from albums a right join tracks t on t.album_id = a.id group by a.id 

Answer 1

 DB[:albums___a]. right_join(:tracks___t, :album_id=>:id). select_group(:a__id). select_more{count(:t__id)} 

Answer 2

您的问题是左连接找到每个相册ID的曲目ID。 解决方案：

right join

sums的子查询，假设续集支持： left join (select album_id, count(album_id) as count from tracks group by album_id) t on

from albums a, tracks t where t.album_id=a.id而不是连接。