Rails查询-非主列上的联接

class User < ApplicationRecord
  has_many :orders
end

class Order < ApplicationRecord
  belongs_to :user
end

users_with_orders = User.joins(:orders)

# 错误的联接条件
users_with_orders = User.joins(:orders).where("users.name = orders.user_name")

# 正确的联接条件
users_with_orders = User.joins(:orders).where("users.id = orders.user_id")

# 添加索引
add_index :orders, :user_id

# 优化查询条件
users_with_orders = User.joins(:orders).where("orders.created_at > ?", 1.week.ago)

# 假设我们有两个表：users 和 orders
class User < ApplicationRecord
  has_many :orders
end

class Order < ApplicationRecord
  belongs_to :user
end

# 查询所有用户及其订单信息
users_with_orders = User.joins(:orders)

# 输出结果
users_with_orders.each do |user|
  puts "User: #{user.name}"
  user.orders.each do |order|
    puts "  Order ID: #{order.id}, Amount: #{order.amount}"
  end
end