Question

我正在关注一个railscast剧集，但我正在使用postgresql并且收到了group_by错误：

PG::Error: ERROR:  column "ratings.created_at" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: SELECT created_at, sum(score) as total_score FROM "ratings" ...
               ^
: SELECT created_at, sum(score) as total_score FROM "ratings"  WHERE ("ratings"."created_at" BETWEEN '2014-01-02 00:00:00.000000' AND '2014-01-23 13:43:06.187741') GROUP BY date(created_at)

我应该如何修改下面的代码以包含group_by created_at

def self.chart_data(start = 3.weeks.ago)
 total_votes = votes_by_day(start)
 (start.to_date..Date.today).map do |date|
 {
  created_at: date,
  total_score: total_prices[date] || 0
 }
 end
end

def self.votes_by_day(start)
 ratings = where(created_at: start.beginning_of_day..Time.zone.now)
 ratings = ratings.group("date(created_at)")
 ratings = ratings.select("created_at, sum(score) as total_score")
 ratings.each_with_object({}) do |rating, scores|
  scores[rating.created_at.to_date] = rating.total_score
 end
end

Answer 1

您的group by子句和您的select子句具有不同的属性。如果您按＆＃34; date（created_at）＆＃34;进行分组然后你就不能再选择＆＃34; created_at。＆＃34;

def self.votes_by_day(start)
  ratings = where(created_at: start.beginning_of_day..Time.zone.now)
  ratings = ratings.group("date(created_at)")
  ratings = ratings.select("date(created_at), sum(score) as total_score")
  ratings.each_with_object({}) do |rating, scores|
  scores[rating.created_at.to_date] = rating.total_score
end

如何添加group_by来修复postgresql group_by错误

1 个答案: