ActiveRecord条件顺序子句
我需要对任务列表进行排序:ActiveRecord条件顺序子句,activerecord,conditional,Activerecord,Conditional,我需要对任务列表进行排序: |----------------------------------------------------------------------| | title | priority | due_at | | ---------------------------------|-------------|---------------------| | Mow the lawn
|----------------------------------------------------------------------|
| 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 |
|----------------------------------------------------------------------|
order子句应按优先级对过期任务进行排序,其他所有任务应按到期时间进行排序,例如,生成的订单应为
- 修剪草坪
- 烤蛋糕
- 打电话给妈妈
- 记住你不喜欢猫
- 喂猫
@tasks
中的任务数组,您可以执行以下操作:
@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)
如果需要任务::ActiveRecord\u关系
,则必须执行以下操作:
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))
我最终得出以下结论(纯SQL,尚未翻译为AR):
选择*
来自任务
订购人
到期日
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