Question

我不完全了解rails scope的作用。 rails查询：

UserDesign.joins(:order_line_items)
     .where('order_line_items.created_at > ?',Date.today-1.month)
     .find(:all,
           :select=>'order_line_items.design_id as id,sum(order_line_items.quantity) as quantity',
           :group=>'order_line_items.design_id',
           :order=>'quantity desc'
     )

返回项目：

 UserDesign Load (0.8ms)  SELECT order_line_items.design_id as id,sum(order_line_items.quantity) as quantity FROM "user_designs" INNER JOIN "order_line_items" ON "order_line_items"."design_id" = "user_designs"."id" WHERE (order_line_items.created_at > '2012-11-12') GROUP BY order_line_items.design_id ORDER BY quantity desc
+-----+----------+
| id  | quantity |
+-----+----------+
| 199 | 65       |
| 196 | 31       |
| 197 | 31       |
| 198 | 30       |
| 204 | 30       |
| 203 | 30       |
+-----+----------+

这是正确的，但只包含两列。与命名范围相同的查询产生：

UserDesign Load (0.7ms)  SELECT order_line_items.design_id as id,sum(order_line_items.quantity) as quantity FROM "user_designs" INNER JOIN "order_line_items" ON "order_line_items"."design_id" = "user_designs"."id" WHERE (order_line_items.created_at > '2012-11-12') GROUP BY order_line_items.design_id ORDER BY quantity desc
UserDesign Load (1.0ms)  SELECT "user_designs".* FROM "user_designs" 
+-----+-------+---
| id  | de... |...
+-----+-------+---
| 196 | aa... |...
| 199 | fd... |...
| 198 | as... |...
| 197 | as... |...
| 203 | Test  |...
| 204 | My... |...
+-----+-------+---

SQL查询是相同的，并返回所有列，但它们的顺序不正确。我想要

使用正确排序的命名范围
将普通查询包装在函数中，但返回所有列

谢谢！

编辑：

为了完整性，这是命名范围：

scope :popular_this_month, lambda{
     joins(:order_line_items)
     .where('order_line_items.created_at > ?',Date.today-1.month)
     .find(:all,
           :select=>'order_line_items.design_id as id,sum(order_line_items.quantity) as quantity',
           :group=>'order_line_items.design_id',
           :order=>'quantity desc'
     )}

Answer 1

在第一种情况下，您传递了一个指定这两列的select选项，因此这两列是返回的。如果您想要更多列，请列出它们（您可以使用table_name。*来获取表的所有列）

在你的第二种情况下，你在命名范围内调用find，这没有任何意义 - 命名范围只是一组条件和选项，你不应该实际做{ {1}}在那里。我怀疑在这种情况下，它忽略了你要找的所有选项。

你想要的更多内容

find

应该与第一个示例的行为相同。

Answer 2

值得一提的是将旧式find语法与较新的where等语法混合使用。

scope :popular_this_month, lambda {
  joins(:order_line_items)
    .where('order_line_items.created_at > ?', Date.today - 1.month)
    .select('order_line_items.design_id as id,sum(order_line_items.quantity) as quantity')
    .group('order_line_items.design_id')
    .order('quantity desc')
}

我认为这可能是问题所在。

Rails范围中的顺序不正确

2 个答案: