如何汇总MongoDB子文档中的每个字段？
要汇总子文档中的每个字段，请使用聚合框架。首先让我们创建一个包含文档的集合-
> db.sumEveryFieldDemo.insertOne(
... {
... "_id":101,
... "PlayerDetails": [
... {"PlayerName":"John","PlayerScore":1000},
... {"PlayerName":"Carol","PlayerScore":2000},
... {"PlayerName":"Sam","PlayerScore":3000}
... ]
... }
... );
{ "acknowledged" : true, "insertedId" : 101 }以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.sumEveryFieldDemo.find().pretty();
这将产生以下输出-
{
"_id" : 101,
"PlayerDetails" : [
{
"PlayerName" : "John",
"PlayerScore" : 1000
},
{
"PlayerName" : "Carol",
"PlayerScore" : 2000
},
{
"PlayerName" : "Sam",
"PlayerScore" : 3000
}
]
}以下是对MongoDB子文档中每个字段求和的查询-
> db.sumEveryFieldDemo.aggregate( [
... { $unwind: "$PlayerDetails" },
... { $group: {
... _id: '$_id',
... sum: { $sum: '$PlayerDetails.PlayerScore' }
... } }
... ] ).pretty();这将产生以下输出-
{ "_id" : 101, "sum" : 6000 }