5

我有几个看起来像这样的文件：

{
        "_id" : ObjectId("50b59cd75bed76f46522c34e"),
        "player_id" : 0,
        "league_id" : 2,
        "results" : [
                {   "discipline" : "football",
                    "score" : 25.15
                },
                {
                        "discipline" : "basketball",
                        "score" : 21.24
                },
                {
                        "discipline" : "cycling",
                        "score" : 68.19
                },]
}

我尝试汇总这些数据。首先展开结果数组，然后只留下“足球”和“自行车”，然后计算平均结果。这部分我做了，它正在工作。我的代码：

db.grades.aggregate(
    {$unwind:"$results"},
    {$match: {$or: [{"results.discipline":"football"},{"results.discipline":"cycling"} ]}},
    {$group:{_id:{player_id:"$player_id",league_id:"$league_id"}, 'average':{$avg:"$results.score"}}},
    )

然后我尝试通过League_id进行聚合，这意味着平均球员在特定联赛中的成绩，添加到上面的代码中： {$group:{_id:"$_id.league_id",aver_league:{$avg:$average}}}

现在代码看起来像：

db.grades.aggregate(
        {$unwind:"$results"},
        {$match: {$or: [{"results.discipline":"football"},{"results.discipline":"cycling"} ]}},
        {$group:{_id:{player_id:"$player_id",league_id:"$league_id"}, 'average':{$avg:"$results.score"}}},
{$group:{_id:"$_id.league_id",aver_league:{$avg:$average}}}
        )

控制台显示：出JavaScript execution failed: ReferenceError: $average is not defined.了什么问题？我在哪里做错了？是否可以聚合_id.league_id？

4

1 回答 1

4

试试这个管道：

[
 {$unwind:"$results"}, 
 {$match: {"results.discipline":{$in:["football", "basketball"]}}}, 
 {$group{_id:{player_id:"$player_id",league_id:"$league_id"}, 'average':{$avg:"$results.score"}}} 
]

它适用于您的文档：

{
"result" : [
    {
        "_id" : {
            "player_id" : 0,
            "league_id" : 2
        },
        "average" : 23.195
    }
],
"ok" : 1
}

UPD。如果你想再次分组，通过League_id：

[{$unwind:"$results"}, 
{$match: {"results.discipline":{$in:["football", "basketball"]}}}, 
{$group:{_id:{player_id:"$player_id",league_id:"$league_id"}, 'average':{$avg:"$results.score"}  }}, 
{$group:{_id:"$_id.league_id", 'average':{$avg:"$average"}  }} ]

{ "result" : [ { "_id" : 2, "average" : 23.195 } ], "ok" : 1 }
于 2013-06-17T11:19:35.137 回答