db.collections.find()
{ "_id" : ObjectId("55b0c2a0339bf8d00ab0bade"), "score" : 46, "playerid" : "45"}
{ "_id" : ObjectId("55b0c2de339bf8d00ab0badf"), "score" : 88, "playerid" : "45"}
{ "_id" : ObjectId("55b0cbca17f398f4281ab931"), "score" : 46, "playerid" : "99"}
{ "_id" : ObjectId("55b15ababe2df0f430d1cb93"), "score" : 89, "playerid" : "45"}
我想要做的事情是获取所有最高分数的文档。如果同一位玩家出现多次,则获取该特定玩家得分最高的文档。
结果应该是这样的:
{ "_id" : "55b0cbca17f398f4281ab931", "score" : 46 }
{ "_id" : "55b15ababe2df0f430d1cb93", "score" : 89 }
这就是我卡住的地方:
db.players.aggregate([
{ "$group": {
"_id": "$playerid",
score: { $max: "$score" }
} }
])
返回:
{ "_id" : "99", "score" : "46" }
{ "_id" : "45", "score" : "89" }
现在,这是正确的。但我只需要ObjectID。