Question

我有以下Query，它根据IDs

数组提取结果集

User.joins(:memberships).
     where(plan_memberships: { user_id: attendee_ids, plan_id: plan.id })

现在我想做另一个排除attendee_ids的调用，然后继续上面的结果，先用attendee_ids保留结果的顺序，然后再保留结果。

有没有办法先根据某些ID保留结果的顺序，然后显示剩余的结果？

Answer 1

您可以尝试注入一些SQL来涵盖您的排除案例。

User.joins(:memberships).
     where(plan_memberships: { user_id: attendee_ids, plan_id: plan.id }).
     where('plan_memberships.user_id not in (?)', banned_user_ids)

注意：根据您选择的数据库，这可能会有所不同

Answer 2

我认为在您的情况下，最好的方法是通过两个数据库查询单独检索结果。

common_scope = User.joins(:memberships).where(plan_memberships: { plan_id: plan.id })

excluded = common_scope.where.not(plan_memberships: { user_id: attendee_ids })
encluded = common_scope.where(plan_memberships: { user_id: attendee_ids })

all_sorted = excluded + encluded

Answer to additional question:

如果您想要检索一定数量的记录，可以这样做：

common_scope = User.joins(:memberships).where(plan_memberships: { plan_id: plan.id })
excluded_scope = common_scope.where.not(plan_memberships: { user_id: attendee_ids })
encluded_scope = common_scope.where(plan_memberships: { user_id: attendee_ids })

number = 3

excluded = excluded_scope.limit(number)
size = excluded.size

if size < number
  encluded = encluded_scope.limit(number - size)
  all_sorted = excluded + encluded
else
  all_sorted = excluded
end

Answer 3

如果您使用的是MySql，则可以选择根据数组中的ID保留订单。

field(user_id, [array of ids])

有关详情，请点击此处http://www.electrictoolbox.com/mysql-order-specific-field-values/

Rails通过排除某些ID来加入

3 个答案: