如何找到具有特定关联值的所有记录？

Question

我有一个 property 模型 belongs_to :property_type。

我想在我的 Property 模型上创建一个范围，以查找特定 property_type 的所有记录。

如何找到所有 property 条带 property_type.name == "Residential" 的记录？

我试过以下方法：

> Property.where('property_type.name = "Residential"').count
   (5.4ms)  SELECT COUNT(*) FROM "properties" WHERE (property_type.name = "Residential")
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "property_type"
LINE 1: SELECT COUNT(*) FROM "properties"  WHERE (property_type.name...

还有这个：

> Property.where('property_types.name = "Residential"').count
   (1.8ms)  SELECT COUNT(*) FROM "properties" WHERE (property_types.name = "Residential")
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "property_types"
LINE 1: SELECT COUNT(*) FROM "properties"  WHERE (property_types.nam...

Answer 1

您可以使用联接来过滤 property_type

Property.joins(:property_type).where(property_types: {name: "Residential"}).count

或

Property.joins(:property_type).where("property_types.name = ?", "Residential").count