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问题描述
我有2个模型(锻炼，设备)，并且属于许多关系.如果使用Workout.find(:all, :joins => :equipment, :conditions => "equipment.id = 5")，它可以工作，但是如果使用Workout.find(:all, :joins => :equipment, :conditions => "equipment.id = null")，它不会返回没有关联的记录.有什么想法吗?
I have 2 models (Workout, Equipment) in a has and belongs to many relationship. If I use Workout.find(:all, :joins => :equipment, :conditions => "equipment.id = 5") it works, but if I use Workout.find(:all, :joins => :equipment, :conditions => "equipment.id = null") it doesn't return the records with no association. Any ideas?
推荐答案
请稍等一下.
Workout.joins("left join equipments e on workouts.id = e.workouts_id").where("e.id is null")
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