Jeremy-san;
Thank you for your reply.
I was solved by your advice!
I choise method of #select_append and alias feature for my code.
2016年3月9日水曜日 12時02分40秒 UTC+9 Jeremy Evans:
>
> On Tuesday, March 8, 2016 at 6:44:32 PM UTC-8, MATSUSHITA Kohei wrote:
>>
>> Hi, sequel developer. This product is very great.
>>
>> I have a question about the Model#association_join with 3 tables.
>>
>> In the following code, is there any way to retrieve created_at of Parent?
>>
>> ```
>> Parent.first.created_at
>> => 2016-03-09 09:11:25 +0900
>> GrandChild.first.created_at
>> => 2016-03-09 09:11:30 +0900
>>
>> r = Parent.association_join(:child => :grand_child).first
>> r.class
>> => Parent
>> r.created_at
>> => 2016-03-09 09:11:30 +0900 ## OMG! this is GrandChild's value
>> ```
>>
>> I guess, this behavior is non-intuitive.
>>
>> Currently, I have a workaround, using Alias feature.
>>
>> ```
>> r = Parent.select_append(Sequel.as(Sequel.qualify(:parents, :created_at),
>> :hoge)).association_join(:child => :grand_child).first
>> r.created_at
>> => 2016-03-09 09:11:30 +0900
>> r[:hoge]
>> => 2016-03-09 09:11:25 +0900 ## Great! (but cannot use #hoge ...)
>> ```
>>
>
> Sequel's default selection is *, so all columns from all tables. Due to
> how the adapters are implemented, in the case of multiple columns with the
> same name, the last entry with the name will be used. Your options are:
>
> 1) Explicitly alias all columns:
>
> p = Parent.select_all(:parents).select_append(:child__name___child_name,
> :child__created_at___child_created_at, ...).association_join(:child =>
> :grand_child).first
> p.created_at
> p[:grand_child_created_at]
>
> 2) Use eager_graph:
>
> p = Parent.eager_graph(:child=>:grand_child).all.first
> p.created_at
> p.child.grand_child.created_at
>
> 3) Use eager_graph with graph_each extension:
>
> p =
> Parent.eager_graph(:child=>:grand_child).extension(:graph_each).clone(:eager_graph=>nil).all.first
> p[:parent][:created_at]
> p[:grand_child][:created_at]
>
> 4) Use eager_graph with ungraphed extension:
>
> p = Parent.eager_graph(:child=>:grand_child).ungraphed.first
> p.created_at
> p[:grand_child_created_at]
>
> Note that if you want to do an INNER JOIN (as association_join does)
> instead of a LEFT OUTER JOIN (as eager_graph does), you can do:
>
> Parent.eager_graph_with_options({:child=>:grand_child},
> :join_type=>:inner)
> # instead of
> Parent.eager_graph(:child=>:grand_child)
>
> Thanks,
> Jeremy
>
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