Hi, I'm trying to do some more elaborated queries with datamapper, but I'm
having some difficulties.

# Group By

I tried to count all my Addresses group by their Users (A User can have many
addresses)

The result would be something like:

[[Jack DMObject, 3],
[Maria DMObject, 4],
[Nina DMObject, 2]]

An array of arrays, with the datamapper object and the count. From what I
read in the docs, It seems that you can only count a given object, not group
them.

http://datamapper.org/docs/find

# Subselect

Select most recent addresses for each user.

select a.* from address a
where a.creation_date = (select max(sub.creation_date) from address sub
where sub.id_user = a.id_user)

The question here is: How to correlate subqueries?

# Eager Loading

This last one could be a mapping error, but I tried to load a single

Company.all.each do | company |
     company.employees.each do |emploee|
           print employee.address # this is always nil
     end
end

I searched in the group, and looks like there are other guys out there with
problem to load deep graphs of objects.

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