Question

我想查询哪里得到与D类关系的所有A类，具有特定名称（D类具有名称列）。但是之间还有B类和C类，实际上我不知道如何通过连接和合并来处理它。

关系如下：

class Appointment
 has_many :booked_classes
 has_many :classes, through: :booked_classes
end

class BookedClass
 belongs_to :Appointment
 belongs_to :Class
end

class Class
 belongs_to :Teacher
 has_many: BookedClasses
end

class Teacher
 has_many :Appointmentss, through :Clasesses
 has_many :Classes
end

Answer 1

你可以试试这个：

Appointment.joins(classes: [:teacher]).where(teachers: { name: "your_name" }) #"your_name" is the name to be matched with the value in name column of Ds table

Answer 2

使用includes method

示例：

Article.includes(:category, :comments)

ActiveRecord通过多个关系查询

2 个答案: