Question

Order has_many TypeLogistic但重要的是...... Order无法拥有TypeLogistic。 Order和＆amp; TypeLogistic具有status_id属性。我想找到所有uniq Order记录，其中：

order.status_id = 4，如果未满足此主要条件，则忽略有关儿童的任何内容
如果order确实有孩子type_logistics，那么所有子type_logistics必须有status_id 1或2（不是任何其他数字而不是{ {1}}）

换句话说......这些是可以找到的记录

null

这些是无法找到的记录

Order
  status_id = 4
  TypeLogistics
    1 - status_id = 1

Order
  status_id = 4
  TypeLogistics
    1 - status_id = 2

Order
  status_id = 4
  TypeLogistics
    1 - status_id = 1
    2 - status_id = 2

Order
  status_id = 4

我编写了一段可行的代码，但它很笨重，因为它使用# because order.status_id != 4 Order status_id = 1 TypeLogistics 1 - status_id = 1 # because type_logistic child does not have a status_id that's 1 or 2 Order status_id = 4 TypeLogistics 1 - status_id = nil # because type_logistic child does not have a status_id that's 1 or 2 Order status_id = 4 TypeLogistics 1 - status_id = 3 # because not all type_logistic children have a status_id that's 1 or 2 Order status_id = 4 TypeLogistics 1 - status_id = 1 2 - status_id = nil # because not all type_logistic children have a status_id that's 1 or 2 Order status_id = 4 TypeLogistics 1 - status_id = 2 2 - status_id = 3而非纯select查询。救救我？

工作，SUB-PAR代码

where

Answer 1

使用joins可以查询已加入的关联。 preload将急切加载type_logistics（如果存在满足where("type_logistics.status_id IN ( ? )", [1,2])查询中指定的条件。 preload的行为大多与includes相似。

@orders = Order.joins(:type_logistics).preload(:type_logistics).where("orders.status_id = ?", 4).where("type_logistics.status_id IN ( ? )", [1,2]).uniq

Rails根据子属性查询父项（如果子项存在，并查看所有子项）

1 个答案: