Complex custom hasMany relationship

1

I have a database structure like so:

> Contracts hasMany ContractsTitles
> ContractsTitles hasMany Rates
> Rates belongsTo Formats

For a given Contract, I would like to know how many distinct Formats are assigned to it via these relationships. For example a query like this:

SELECT contracts_titles.contract_id AS contract_id, formats.name AS format FROM rates
LEFT JOIN formats on rates.format_id = formats.id
LEFT JOIN contracts_titles ON rates.contracts_title_id = contracts_titles.id
GROUP BY contracts_titles.contract_id, formats.id;

That would produce a table like:

contract_id | format
--------------------------
1           | Small
1           | Medium
1           | Large
2           | Medium
3           | Small
3           | Large

So what I would like is to be able to quickly access this data as if it were a contain, like if I did ->contain([‘AssignedFormats']) then Contract 1 would have the property assigned_formats with Small, Medium and Large entries.

Is there a way to define this as a relationship, or some other sensible way to make this easily accessible from the Contracts table? Thanks