我正在尝试撰写MongoDB查询...我的目标是按country检索按rating排序的玩家记录列表，然后返回only每个国家/地区的第n个评分玩家(所以评价最高，或第三最佳评价等)。我已经完成了第一部分:db.getCollection('players').find({event:'open'}).sort({country:1,rating:-1});更新这是两个国家的样本，每个国家有三名球员，按等级排序:第一组:{"id":400041,"name":"AdamsMichael","rating":2727,"country":"England","event":"open"}

1.基础分BaseRating=ProblemScorce∗0.5+ratingScorce∗0.4+BlogScore∗0.1BaseRating=ProblemScorce*0.5+ratingScorce*0.4+BlogScore*0.1BaseRating=ProblemScorce∗0.5+ratingScorce∗0.4+BlogScore∗0.1ProblemScorce=PassPloblemSumProblemScorce=PassPloblemSumProblemScorce=PassPloblemSumratingScorce=(AtcodeRating+Codefor

1.基础分BaseRating=ProblemScorce∗0.5+ratingScorce∗0.4+BlogScore∗0.1BaseRating=ProblemScorce*0.5+ratingScorce*0.4+BlogScore*0.1BaseRating=ProblemScorce∗0.5+ratingScorce∗0.4+BlogScore∗0.1ProblemScorce=PassPloblemSumProblemScorce=PassPloblemSumProblemScorce=PassPloblemSumratingScorce=(AtcodeRating+Codefor