Question

在我的Rails 4.1应用程序中，我构建一个查询，通过多态关系（买方）的属性（名称）查找我的集合（订单）中的记录。这个多态有2个可能的表，所以我使用2 LEFT JOINS + COALESCE来合并属性。然后尝试在where子句中使用COALESCE中的值。

我的ActiveRecord模型中的方法如下所示：

class Order
  ...
  scope :join_by_buyer_name, -> { select("stock_orders.*", "COALESCE(core_customers.business_name, core_entities.name) AS buyer_name")
      .joins("LEFT JOIN core_customers ON stock_orders.buyer_id = core_customers.id AND stock_orders.buyer_type='Core::Customer'")
      .joins("LEFT JOIN core_entities ON stock_orders.buyer_id = core_entities.id AND stock_orders.buyer_type='Core::Entity'")
    }
  ...

  def find_by_buyer_name(term)
    all.join_by_buyer_name.where("buyer_name LIKE ?", term)
  end


end

执行ActiveRecord查询时，它看起来像这样

SELECT stock_orders.*, COALESCE(core_customers.business_name, core_entities.name) AS buyer_name
FROM `stock_orders`
LEFT JOIN core_customers ON stock_orders.buyer_id = core_customers.id AND stock_orders.buyer_type='Core::Customer'
LEFT JOIN core_entities ON stock_orders.buyer_id = core_entities.id AND stock_orders.buyer_type='Core::Entity'
WHERE `stock_orders`.`type` IN ('Stock::SalesOrder') AND (buyer_name LIKE "blah")

直到最近这个工作，但我已经开始收到以下错误：

Mysql2::Error: Unknown column 'buyer_name' in 'where clause': SELECT stock_orders.*, COALESCE等等

它非常适合按COALESCE值排序 - 即collection.order("buyer_name asc")，直到最近查询工作完全正确...

我不确定发生了什么变化，并且无法在Rails或Mysql文档中看到任何内容。你能看出这里有什么问题吗？请帮忙！

Answer 1

您不能使用从ALIAS子句创建的WHERE子句中的SELECT。请改用计算列，

AND (COALESCE(core_customers.business_name, core_entities.name) LIKE "blah")

如果你想使用ALIAS，你必须将它包装在子查询中，如下面的查询，

SELECT *
FROM
     (
     SELECT stock_orders.*, 
           COALESCE(core_customers.business_name, core_entities.name) AS buyer_name
     FROM `stock_orders`
          LEFT JOIN core_customers 
                ON stock_orders.buyer_id = core_customers.id 
                     AND stock_orders.buyer_type='Core::Customer'
          LEFT JOIN core_entities 
                     ON stock_orders.buyer_id = core_entities.id 
                     AND stock_orders.buyer_type='Core::Entity'
     ) subquery
WHERE `type` IN ('Stock::SalesOrder') 
      AND (buyer_name LIKE "blah")

Mysql2错误 - 在where子句中使用COALESCE，Unknown列

1 个答案: