[英]MongoDB double $group aggregation
我有幾個文檔看起來像這樣:
{
"_id" : ObjectId("50b59cd75bed76f46522c34e"),
"player_id" : 0,
"league_id" : 2,
"results" : [
{ "discipline" : "football",
"score" : 25.15
},
{
"discipline" : "basketball",
"score" : 21.24
},
{
"discipline" : "cycling",
"score" : 68.19
},]
}
我嘗試聚合這些數據。 首先展開結果數組,然后只留下“ 足球 ”和“ 騎自行車 ”,接下來計算平均結果。 這部分我做了,它正在發揮作用。 我的代碼:
db.grades.aggregate(
{$unwind:"$results"},
{$match: {$or: [{"results.discipline":"football"},{"results.discipline":"cycling"} ]}},
{$group:{_id:{player_id:"$player_id",league_id:"$league_id"}, 'average':{$avg:"$results.score"}}},
)
然后我嘗試通過league_id進行聚合,這意味着,普通玩家會在特定聯盟中產生結果,添加到上面的代碼: {$group:{_id:"$_id.league_id",aver_league:{$avg:$average}}}
現在代碼看起來像:
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}}}
)
控制台顯示: JavaScript execution failed: ReferenceError: $average is not defined.
怎么了? 我在哪里弄錯了? 可以通過_id.league_id
嗎?
試試這個管道:
[
{$unwind:"$results"},
{$match: {"results.discipline":{$in:["football", "basketball"]}}},
{$group{_id:{player_id:"$player_id",league_id:"$league_id"}, 'average':{$avg:"$results.score"}}}
]
它適合我的文檔:
{
"result" : [
{
"_id" : {
"player_id" : 0,
"league_id" : 2
},
"average" : 23.195
}
],
"ok" : 1
}
UPD。 如果你想再次分組,請通過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 }
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