原文链接：https://www.mkyong.com/mongodb/mongodb-group-count-and-sort-example/
1. Test Data
A whois_range collection, containing many records.
> db.whois_range.find();
{
"_id" : 1,
"country" : "us",
"source" : "ARIN",
"status" : "NEW",
"createdDate" : ISODate("2016-05-03T08:52:32.434Z")
},
{
"_id" : 2,
"country" : "us",
"source" : "ARIN",
"status" : "NEW",
"createdDate" : ISODate("2016-05-03T09:52:32.434Z")
},
{
"_id" : 3,
"country" : "cn",
"source" : "APNIC",
"status" : "NEW",
"createdDate" : ISODate("2016-05-03T10:52:32.434Z")
},
{
"_id" : 4,
"country" : "eu",
"source" : "RIPE",
"status" : "NEW",
"createdDate" : ISODate("2016-05-03T10:52:32.434Z")
},
{...}
P.S “Source” = RIPE, AFRINIC, KRNIC, LACNIC, APNIC, JPNIC and ARIN
2. Group and Count example
Group by “source”, and count the total number of “source”.
> db.whois_range.aggregate([
{"$group" : {_id:"$source", count:{$sum:1}}}
])
{ "_id" : "RIPE", "count" : 29270 }
{ "_id" : "AFRINIC", "count" : 1326 }
{ "_id" : "KRNIC", "count" : 105 }
{ "_id" : "LACNIC", "count" : 5889 }
{ "_id" : "APNIC", "count" : 6644 }
{ "_id" : "JPNIC", "count" : 167 }
{ "_id" : "ARIN", "count" : 25429 }
3. Group by multiple ids example
Group by two ids: “source” and “status”.
> db.whois_range.aggregate([
{"$group" : {_id:{source:"$source",status:"$status"}, count:{$sum:1}}} ])
])
{ "_id" : { "source" : "RIPE", "status" : "NEW" }, "count" : 29260 }
{ "_id" : { "source" : "RIPE", "status" : "ERROR" }, "count" : 10 }
{ "_id" : { "source" : "LACNIC", "status" : "NEW" }, "count" : 5889 }
{ "_id" : { "source" : "KRNIC", "status" : "NEW" }, "count" : 105 }
{ "_id" : { "source" : "APNIC", "status" : "NEW" }, "count" : 6644 }
{ "_id" : { "source" : "AFRINIC", "status" : "NEW" }, "count" : 1326 }
{ "_id" : { "source" : "JPNIC", "status" : "NEW" }, "count" : 167 }
{ "_id" : { "source" : "ARIN", "status" : "NEW" }, "count" : 25420 }
{ "_id" : { "source" : "ARIN", "status" : "DONE" }, "count" : 9 }
3. Group, Count, and Sort example
3.1 Group by two ids: “source” and “status”, count the total number of records, and sort by “source”.
> db.whois_range.aggregate([
{"$group" :
{_id:{source:"$source",status:"$status"}, count:{$sum:1}}
},
{$sort:{"_id.source":1}}
])
{ "_id" : { "source" : "AFRINIC", "status" : "NEW" }, "count" : 1326 }
{ "_id" : { "source" : "APNIC", "status" : "NEW" }, "count" : 6644 }
{ "_id" : { "source" : "ARIN", "status" : "NEW" }, "count" : 25420 }
{ "_id" : { "source" : "ARIN", "status" : "DONE" }, "count" : 9 }
{ "_id" : { "source" : "JPNIC", "status" : "NEW" }, "count" : 167 }
{ "_id" : { "source" : "KRNIC", "status" : "NEW" }, "count" : 105 }
{ "_id" : { "source" : "LACNIC", "status" : "NEW" }, "count" : 5889 }
{ "_id" : { "source" : "RIPE", "status" : "NEW" }, "count" : 29260 }
{ "_id" : { "source" : "RIPE", "status" : "ERROR" }, "count" : 10 }
3.2 Sort by “count”, descending order.
> db.whois_range.aggregate([
{"$group" :
{_id:{source:"$source",status:"$status"}, count:{$sum:1}}
},
{$sort:{"count":-1}}
])
{ "_id" : { "source" : "RIPE", "status" : "NEW" }, "count" : 29260 }
{ "_id" : { "source" : "ARIN", "status" : "NEW" }, "count" : 25420 }
{ "_id" : { "source" : "APNIC", "status" : "NEW" }, "count" : 6644 }
{ "_id" : { "source" : "LACNIC", "status" : "NEW" }, "count" : 5889 }
{ "_id" : { "source" : "AFRINIC", "status" : "NEW" }, "count" : 1326 }
{ "_id" : { "source" : "JPNIC", "status" : "NEW" }, "count" : 167 }
{ "_id" : { "source" : "KRNIC", "status" : "NEW" }, "count" : 105 }
{ "_id" : { "source" : "RIPE", "status" : "ERROR" }, "count" : 10 }
{ "_id" : { "source" : "ARIN", "status" : "DONE" }, "count" : 9 }