按照created_at和updated_at的顺序选择记录两次

Question

我想根据mysql表中的两个字段选择一个记录两次。

例如我的表有下列数据：

name, created_at, updated_at 
"Baran", "2013-09-10 23:56:56", "2013-10-10 23:00:00" 

我想降序排列的结果集：

name,date 
Baran,"2013-10-10 23:00:00" 
Baran,"2013-09-10 23:56:56" 

是有可能与否，如果是的话，请指点我如何能实现这个？

Answer 1

(SELECT name, created_at as [date] FROM mytable) 
    UNION all 
(SELECT name, updated_at as [date] FROM mytable) 
    ORDER BY name, [date] desc; 

Answer 2

您可以选择您的记录像往常一样在Ruby中创建了“重复”：

User.all.flat_map { |user| 
    [ 
    {name: user.name, date: user.created_at}, 
    {name: user.name, date: user.updated_at} 
    ] 
} 
#=> [{:name=>"Baran", :date=>"2013-09-10 23:56:56"}, {:name=>"Baran", :date=>"2013-10-10 23:00:00"}]