On Wednesday, December 19, 2012 12:29:41 PM UTC-8, Geraldo Lopes de Souza
wrote:
>
> Thank you Jeremy.
>
> I'm playing with dataset syntax to choose which one to use.
>
> I rewrote as:
>
> ds = DB[:employees___employee].select(:first_name, :last_name,
> Sequel::SQL::Function.new('upper',
> :last_name).as(:upper_last_name)).graph(:employees,
> {:employee_id => :manager_id}, {:table_alias => :manager, :select =>
> [:first_name ]})
>
This is a fine way to do that.
> If you use set_graph_aliases to select which fields you want kind of
> defeats the advantage of the graph that is no need to alias
> everything.
>
Correct. set_graph_aliases should only be used in cases where you need a
lot of control over the graph. In most cases, you can use Dataset#select
and the :select option for the parts that they handle, and
add_graph_aliases for the other parts.
Originally, you could not do what you are doing now, and
set_graph_aliases/add_graph_aliases was necessary for advanced cases. Now,
in some cases graph's :select option can be used instead of
*_graph_aliases. However, not in all cases. For example, if you wanted to
run the upper function on manager.first_name, you couldn't use :select to
do that. You would need to do:
ds = DB[:employees___employee].
select(:first_name, :last_name,
Sequel::SQL::Function.new('upper',
:last_name).as(:upper_last_name)).graph(:employees,
{:employee_id => :manager_id}, {:table_alias => :manager, :select =>
[]}).add_graph_aliases(:manager_name=>[:manager, :first_name,
Sequel.function(:upper, :manager__first_name)])
Note that I'm using select on the main dataset. and :select option on
> the graphed one to choose which fields I want. Is that allowed ?
>
Yes.
Thanks,
Jeremy
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