Rails 3 在多个日期范围内查询答案

【问题标题】：Rails 3 query in multiple date rangesRails 3 在多个日期范围内查询
【发布时间】：2012-04-06 10:29:09
【问题描述】：

假设我们有一些日期范围，例如：

ranges = [
          [(12.months.ago)..(8.months.ago)],
          [(7.months.ago)..(6.months.ago)],
          [(5.months.ago)..(4.months.ago)],
          [(3.months.ago)..(2.months.ago)],
          [(1.month.ago)..(15.days.ago)]
         ]

还有一个带有:created_at 属性的Post 模型。

我想查找created_at 值在此范围内的帖子，因此目标是创建如下查询：

SELECT * FROM posts WHERE created_at 
    BETWEEN '2011-04-06' AND '2011-08-06' OR
    BETWEEN '2011-09-06' AND '2011-10-06' OR
    BETWEEN '2011-11-06' AND '2011-12-06' OR
    BETWEEN '2012-01-06' AND '2012-02-06' OR
    BETWEEN '2012-02-06' AND '2012-03-23';

如果你只有一个这样的范围：

range = (12.months.ago)..(8.months.ago)

我们可以这样查询：

Post.where(:created_at => range)

查询应该是：

SELECT * FROM posts WHERE created_at 
    BETWEEN '2011-04-06' AND '2011-08-06';

有没有办法使用像Post.where(:created_at => range) 这样的符号进行此查询？

构建此查询的正确方法是什么？

谢谢

【问题讨论】：

标签： ruby-on-rails-3 activerecord active-relation

【解决方案1】：

它对paren有点激进，但准备潜入兔子洞

ranges = [
          ((12.months.ago)..(8.months.ago)),
          ((7.months.ago)..(6.months.ago)),
          ((5.months.ago)..(4.months.ago)),
          ((3.months.ago)..(2.months.ago)),
          ((1.month.ago)..(15.days.ago))
         ]
table = Post.arel_table
query = ranges.inject(table) do |sum, range|
  condition = table[:created_at].in(range)
  sum.class == Arel::Table ? condition : sum.or(condition)
end

那么，query.to_sql 应该等于

(((("sessions"."created_at" BETWEEN '2011-06-05 12:23:32.442238' AND '2011-10-05 12:23:32.442575' OR "sessions"."created_at" BETWEEN '2011-11-05 12:23:32.442772' AND '2011-12-05 12:23:32.442926') OR "sessions"."created_at" BETWEEN '2012-01-05 12:23:32.443112' AND '2012-02-05 12:23:32.443266') OR "sessions"."created_at" BETWEEN '2012-03-05 12:23:32.443449' AND '2012-04-05 12:23:32.443598') OR "sessions"."created_at" BETWEEN '2012-05-05 12:23:32.443783' AND '2012-05-21 12:23:32.443938')

你应该可以只做 Post.where(query)

编辑

你也可以这样做：

range_conditions = ranges.map{|r| table[:created_at].in(r)}
query = range_conditions.inject(range_conditions.shift, &:or)

保持简洁一点

【讨论】：

【解决方案2】：

建议你试试纯字符串形式：

# e.g. querying those in (12.months.ago .. 8.months.ago) or in (7.months.ago .. 6.months.ago)
Post.where("(created_at <= #{12.months.ago} AND created_at >= #{8.months.ago} ) OR " + 
  "(created_at <= #{7.months.ago} AND created_at >= #{6.months.ago} )" )

【讨论】：

我们不需要在Arel身边写sql。

【解决方案3】：

在你的情况下，我建议使用 mysql IN 子句

Model.where('created_at IN (?)', ranges)

【讨论】：