mysql - 为返回一些空行的分组查询填写空白日期

Question

在 n 天的过程中，我一直在努力获取数据以进行统计。我真的不在乎输出格式，只要它按顺序显示日期，并将值显示为数组... all_data 查询(如下)将获取确定时间段内的所有值，但它不会' t 为没有值的日期创建行。目标是能够输出:

# Get 10 (for example) days of data->

[
    {date:'datetime-day-ago-10', values: [{foo:'bar', foo2:'bar2', foo3:'bar'3}]}
    {date:'datetime-day-ago-9', values: [{foo:'bar', foo2:'bar2', foo3:'bar'3}]}
    {date:'datetime-day-ago-8', values: []}
    {date:'datetime-day-ago-7', values: [{foo:'bar', foo2:'bar2', foo3:'bar'3}]}
    {date:'datetime-day-ago-6', values: []}
    {date:'datetime-day-ago-5', values: []}
    {date:'datetime-day-ago-4', values: [{foo:'bar', foo2:'bar2', foo3:'bar'3}]}
    {date:'datetime-day-ago-3', values: [{foo:'bar', foo2:'bar2', foo3:'bar'3}]}
    {date:'datetime-day-ago-2', values: []}
    {date:'datetime-day-ago-1', values: []}
]

这是我此时使用的方法。

def counts

    from = params[:days].to_i.days.ago.to_time.beginning_of_day
    to = 0.days.ago.to_time.end_of_day

    all_data = current_user.values.all
                .where(field_id: params[:field_id], created_at: from .. to)
                .where.not(input: nil)
                .order(input: :desc)
                .group_by { |value| value['created_at'].to_date}
                .map {|k,v| [k,v]}

    grouped = (0..params[:days].to_i-1).to_a.inject([]) do |memo, i|
        if all_data[i].present?
            date = all_data[i][0].to_time
            values = all_data[i][1].group_by { |value| value.input }.map { |k, v| {input:k, count:v.length} }.sort! { |x,y| x['input'] <=> y['input']}
            total = 0
            values.each do |value|
                total = total + value[:count]
            end
        else

            # This is where I can't figure out how to assign a date for rows which have no data.

            date = ((i-params[:days].to_i+1)*-(1)).days.ago.beginning_of_day

        end
        memo << {'date': date, 'total': total || 0, 'values': values || []}
        memo
    end

    grouped = grouped.sort_by { |day| day['date'] }
    render json: grouped
end

# Sample of entire output for 10 days

0: {date: "2015-10-31T00:00:00.000-07:00", total: 15,…} <- 10-31-2015 HAS VALUES
1: {date: "2015-11-01T00:00:00.000-07:00", total: 49,…} <- 11-01-2015 HAS VALUES
2: {date: "2015-11-02T00:00:00.000-08:00", total: 10,…} <- 11-02-2015 HAS VALUES
3: {date: "2015-11-03T00:00:00.000-08:00", total: 21,…} <- 11-03-2015 HAS VALUES
4: {date: "2015-10-30T00:00:00.000-07:00", total: 0, values: []}
5: {date: "2015-10-31T00:00:00.000-07:00", total: 0, values: []}  \
6: {date: "2015-11-01T00:00:00.000-07:00", total: 0, values: []}    -  No matter what I try I can't get these dates to be the 5 days before 10-31-2015...
7: {date: "2015-11-02T00:00:00.000-08:00", total: 0, values: []}  /
8: {date: "2015-11-03T00:00:00.000-08:00", total: 0, values: []}
9: {date: "2015-11-04T00:00:00.000-08:00", total: 0, values: []} <- 11-04-2015 This should appear up there ^ under the last HAS VALUES row 

那么，我怎样才能正确地为空值行创建日期呢？然后我怎样才能确保它们按照正确的顺序排列？就像我说的那样，我对此一头雾水。算法不是我的菜。

Answer 1

可能是，你可以从这边来:

grouped = (from.to_date..to.to_date).each do |dt|
  existing_data = all_data.detect{ |data| data.first == dt }
  if existing_data
    # you code for existing date
  else
    # you code for non-existing date
  end
  # ...
end

# And, I think, it is not required in this case
#grouped = grouped.sort_by { |day| day['date'] }