“Order by” result of “group by” count?

问题

This query

Message.where("message_type = ?", "incoming").group("sender_number").count

will return me an hash.

OrderedHash {"1234"=>21, "2345"=>11, "3456"=>63, "4568"=>100}

Now I want to order by count of each group. How can I do that within the query.

回答1:

The easiest way to do this is to just add an order clause to the original query. If you give the count method a specific field, it will generate an output column with the name count_{column}, which can be used in the sql generated by adding an order call:

Message.where('message_type = ?','incoming')
       .group('sender_number')
       .order('count_id asc').count('id')

回答2:

When I tried this, rails gave me this error

SQLite3::SQLException: no such column: count_id: SELECT  COUNT(*) AS count_all, state AS state FROM "ideas"  GROUP BY state ORDER BY count_id desc LIMIT 3

Notice that it says SELECT ... AS count_all

So I updated the query from @Simon's answer to look like this and it works for me