我需要对任务列表进行排序:
|----------------------------------------------------------------------|
| title | priority | due_at |
| ---------------------------------|-------------|---------------------|
| Mow the lawn | 1 | 2011-09-11 22:00:00 |
| Call mom | 3 | 2010-01-26 09:29:03 |
| Bake a cake | 2 | 2013-09-13 08:45:37 |
| Feed the cat | 2 | 2015-09-12 16:03:51 |
| Remember you don't like the cat | 2 | 2014-03-19 23:00:00 |
|----------------------------------------------------------------------|
订单子句应按优先级对所有过期任务进行排序,所有其他任务按due_at排序,例如:结果顺序应为
答案 0 :(得分:1)
我最终得到了以下内容(纯SQL,尚未翻译成AR):
SELECT *
FROM tasks
ORDER BY
due_at <= Now() DESC,
CASE due_at <= Now() WHEN true THEN priority END ASC,
CASE due_at <= Now() WHEN true THEN due_at END ASC,
CASE due_at <= Now() WHEN false THEN due_at END DESC,
CASE due_at <= Now() WHEN false THEN priority END ASC
答案 1 :(得分:0)
如果你只需要存储在@tasks
中的一系列任务,你可以这样做:
@tasks = Task.where(due_at: 10.years.ago..Time.now).order(:priority)
@tasks += Task.where.not(due_at: 10.years.ago..Time.now).order(:due_at)
如果您需要Task::ActiveRecord_Relation
,则必须执行此操作:
Task.where(id: Task.where(due_at: 10.years.ago..Time.now).
order(:priority).pluck(:id) +
Task.where.not(due_at: 10.years.ago..Time.now).
order(:due_at).pluck(:id))