ActiveRecord查询（包括或加入）

Question

我有两节课：

class Customer 
    has_many :packages
end

class Package 
    belongs_to :customer
end

我怎么能这样做一个查询？

Customer.includes(:packages).where(packages: 'expires_at < Date.current')

通过控制台的示例测试，我得到了它：

Customer Load (26.0ms)  SELECT  "customers".* FROM "customers" INNER JOIN "packages" ON "packages"."customer_id" = "customers"."id" WHERE (packages.expires_at < '2019-03-13') LIMIT $1  [["LIMIT", 11]]
Traceback (most recent call last):
ActiveRecord::StatementInvalid (PG::UndefinedFunction: ERROR:  operator does not exist: integer = uuid)
LINE 1: ...INNER JOIN "packages" ON "packages"."customer_id" = "custome...
                                                             ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
: SELECT  "customers".* FROM "customers" INNER JOIN "packages" ON "packages"."customer_id" = "customers"."id" WHERE (packages.expires_at < '2019-03-13') LIMIT $1
irb(main):003:0>

Answer 1

您可以在引号内传递where表达式并绑定expires_at的值。

Customer.includes(:packages).where('packages.expires_at < ?', Date.current)

Answer 2

你可以这样做：

Customer.includes(:packages).where('packages.expires_at < ?', Date.current).references(:packages)

Answer 3

Customer.joins(:packages).where("packages.expires_at < CURRENT_DATE")

要么

Customer.includes(:packages).where("packages.expires_at < CURRENT_DATE").references(:packages)

Answer 4

你可以这样做：

Customer.includes([:packages]).where(["packages.expires_at < ?', Date.today]).references(:packages).order("Customers.created_at desc")