如何通过另一个字段MongoDB(分组)获得一个字段的distinct计数?
我有以下文件:如何通过另一个字段MongoDB(分组)获得一个字段的distinct计数?,mongodb,mongodb-query,aggregation-framework,pymongo,Mongodb,Mongodb Query,Aggregation Framework,Pymongo,我有以下文件: { "type" : "A", "item" : "I1"} { "type" : "A", "item" : "I2"} { "type" : "A", "item" : "I2"} { "type" : "A&
{ "type" : "A", "item" : "I1"}
{ "type" : "A", "item" : "I2"}
{ "type" : "A", "item" : "I2"}
{ "type" : "A", "item" : "I2"}
{ "type" : "A", "item" : "I3"}
{ "type" : "B", "item" : "I4"}
{ "type" : "B", "item" : "I4"}
{ "type" : "B", "item" : "I5"}
我想找到每个“类型”的不同“项”的计数,如下所示:
{ "type" : "A", "item-count" : 3}
{ "type" : "B", "item-count" : 2}
你知道如何编写MongoDB查询吗?谢谢你可以试试
按类型和项目$group
仅按类型和计数总和$group
db.collection.aggregate([
{
$group: {
_id: {
type: "$type",
item: "$item"
}
}
},
{
$group: {
_id: "$_id.type",
"item-count": { $sum: 1 }
}
}
])