Ruby-on-rails “分组依据”计数的“排序依据”结果？
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"Order by" result of "group by" count?
提问by Mohit Jain
This query
这个查询
Message.where("message_type = ?", "incoming").group("sender_number").count
will return me an hash.
会给我一个哈希值。
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.
现在我想按每组的数量排序。我怎样才能在查询中做到这一点。
回答by Simon Elliston Ball
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:
最简单的方法是在原始查询中添加一个 order 子句。如果给 count 方法一个特定的字段，它会生成一个名为 count_{column} 的输出列，可以在添加订单调用生成的 sql 中使用：
Message.where('message_type = ?','incoming')
.group('sender_number')
.order('count_id asc').count('id')
回答by penner
When I tried this, rails gave me this error
当我尝试这个时，rails 给了我这个错误
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
请注意，它说 SELECT ... AS count_all
So I updated the query from @Simon's answer to look like this and it works for me
所以我更新了@Simon 答案中的查询，看起来像这样，它对我有用
.order('count_all desc')
