Rails 4加入相关表 - 当某些记录没有关联时进行排序

Question

I am using the following:

Vehicle.joins(:supplier, :owner, :model).order("#{sort_column} #{sort_direction}")

which allows me to order the results by attributes in any of the 4 associated models. The problem is when a specific vehicle does not have an association eg a supplier, then no results are returned. Only if all vehicles have all 3 associations will any results show.

Is there an alternative way that the functionality I need can be achieved?

Answer 1

By default rails does inner join. That's why you don't see the records when there is no association.

If you want you can change the type of join by mentioning it explicitly

Vehicle
.joins("LEFT JOIN suppliers on vehicles.supplier_id = suppliers.id")
.joins("LEFT JOIN owners on vehicles.owner_id = owners.id")
.joins("LEFT JOIN models on vehicles.model_id = models.id")
.order("#{sort_column} #{sort_direction}")

I guessed your table_names and foreign_key names based on the association name. Please change it if they are different