问题
I have a Rails app where I'm trying to create a list of parent classes based on the date of their child classes.
right now I have:
orders = Order.where("order_reminders.date < ?", 1.month.from_now)
But I'm receiving an error.
"no such column: order_reminders.date"
I'm sure my problem is with my query but I'm not sure how to fix it.
回答1:
You need to use methods like references, joins, includes or eager_load depending on what you need. The simplest way to determine what to select is to go to the documentation/api and read them.
As for the answer, if order_reminders is defined as an association in Order, just use joins which uses an INNER JOIN by default, meaning it won't return orders without order_reminders which is most probably what you want when you're searching for something.
Order.joins(:order_reminders).where('order_reminders.date < ?', 1.month.from_now)
回答2:
Is order_reminders another table in your app?
If order has_many order_reminders then try this query
Order.joins(:order_reminders).where("order_reminders.date < ?", 1.month.from_now)
来源：https://stackoverflow.com/questions/32940206/rails-where-method-to-find-parent-by-child-attribute