Question

class User
  has_many :calendars
  has_many :cars, through: :calendars
end

class Calendar
  has_many :cars
end

class Car
  # attribute `issued_at`
end

我需要按issued_at的汽车订购用户。因此，根据大孩子的属性issued_at对父母进行排序。

到此为止：

@q = User.active.joins(:cars).order('cars.issued_at').group('users.id')

但是我得到了

column "cars.issued_at" must appear in the GROUP BY clause or be used in an aggregate function

Answer 1

使用distinct而不是group来消除重复项：

@q = User.active.joins(:cars).order('cars.issued_at').distinct

Answer 2

这是复制品仓库：https://github.com/localhostdotdev/bug/tree/ordering-parents-by-grand-children

进行相同的查询时，我没有看到任何错误，则问题必须在您的active范围内。

这是带有scope :active, -> { where(active: true) }的完整查询：

SELECT "users".*
FROM "users"
INNER JOIN "calendars" ON "calendars"."user_id" = "users"."id"
INNER JOIN "cars" ON "cars"."calendar_id" = "calendars"."id"
WHERE "users"."active" = ?
GROUP BY users.id
ORDER BY cars.issued_at
LIMIT ?

我无法重现您的问题。

Rails：按大孩子的属性订购父母

2 个答案: