有几种方法。你可以使用这个方法:

start = @selected_date.beginning_of_day
end = @selected_date.end_of_day
@comments = Comment.where("DATE(created_at) BETWEEN ? AND ?", start, end)

或:

@comments = Comment.where(:created_at => @selected_date.beginning_of_day..@selected_date.end_of_day)

请注意，目前接受的答案在Rails 3中已弃用。你应该这样做:

Comment.where(:created_at => @selected_date.beginning_of_day..@selected_date.end_of_day)

或者，如果你想或必须使用纯字符串条件，你可以这样做:

Comment.where('created_at BETWEEN ? AND ?', @selected_date.beginning_of_day, @selected_date.end_of_day)

如果你只想休息一天，这样做会更容易:

Comment.all(:conditions => ["date(created_at) = ?", some_date])

我个人会创建一个范围，使其更具可读性和可重用性:

在你的评论中。Rb，你可以定义一个范围:

scope :created_between, lambda {|start_date, end_date| where("created_at >= ? AND created_at <= ?", start_date, end_date )}

然后到查询之间创建:

@comment.created_between(1.year.ago, Time.now)

希望能有所帮助。

我认为应该有一个默认的活动记录行为。查询日期很困难，特别是涉及到时区时。

总之，我用:

  scope :between, ->(start_date=nil, end_date=nil) {
    if start_date && end_date
      where("#{self.table_name}.created_at BETWEEN :start AND :end", start: start_date.beginning_of_day, end: end_date.end_of_day)
    elsif start_date
      where("#{self.table_name}.created_at >= ?", start_date.beginning_of_day)
    elsif end_date
      where("#{self.table_name}.created_at <= ?", end_date.end_of_day)
    else
      all
    end
  }

有几种方法。你可以使用这个方法:

start = @selected_date.beginning_of_day
end = @selected_date.end_of_day
@comments = Comment.where("DATE(created_at) BETWEEN ? AND ?", start, end)

或:

@comments = Comment.where(:created_at => @selected_date.beginning_of_day..@selected_date.end_of_day)