在 MongoDB 中跨两列分组?
mongodbdatabasebig data analytics更新于 2026/1/10 6:52:17
要跨两列分组，请使用 $lookup。让我们创建一个包含文档的集合。 −
> db.demo132.insertOne({"CountryName1":"US","CountryName2":"UK",Value:50});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31950468e7f832db1a7f75")
}
> db.demo132.insertOne({"CountryName1":"UK","CountryName2":"AUS",Value:10});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31951d68e7f832db1a7f76")
}
> db.demo132.insertOne({"CountryName1":"AUS","CountryName2":"US",Value:40});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e31952c68e7f832db1a7f77")
}
借助 find() 方法显示集合中的所有文档 −
> db.demo132.find();
这将产生以下输出 −
{ "_id" : ObjectId("5e31950468e7f832db1a7f75"), "CountryName1" : "US", "CountryName2" : "UK", "Value" : 50 }
{ "_id" : ObjectId("5e31951d68e7f832db1a7f76"), "CountryName1" : "UK", "CountryName2" : "AUS", "Value" : 10 }
{ "_id" : ObjectId("5e31952c68e7f832db1a7f77"), "CountryName1" : "AUS", "CountryName2" : "US", "Value" : 40 }
以下是在 MongoDB 中对两列进行分组的查询 −
> db.demo132.aggregate( [
... {
... "$lookup" : {
... "from" : "demo132",
... "localField" : "CountryName1",
... "foreignField" : "CountryName2",
... "as" : "out"
... }
... },
... {
... "$unwind" : "$out"
... },
... {
... "$project" : {
... "_id" : 0,
... "CountryName1" : 1,
... "total" : { "$sum" : [ "$Value", "$out.Value"]}
... }
... }
... ])
这将产生以下输出 −
{ "CountryName1" : "US", "total" : 90 }
{ "CountryName1" : "UK", "total" : 60 }
{ "CountryName1" : "AUS", "total" : 50 }
