Mongodb group and sort

Question

How can I translate the following Sql query for Mongo?:

select a,b,sum(c) csum from coll where active=1 group by a,b order by a 

Is there any way to execute a group and sort query with Mongo?

Answer 1

Inspired by this example on mongo's website.

GENERATE DUMMY DATA:

> db.stack.insert({a:1,b:1,c:1,active:1}) > db.stack.insert({a:1,b:1,c:2,active:0}) > db.stack.insert({a:1,b:2,c:3,active:1}) > db.stack.insert({a:1,b:2,c:2,active:0}) > db.stack.insert({a:2,b:1,c:3,active:1}) > db.stack.insert({a:2,b:1,c:10,active:1}) > db.stack.insert({a:2,b:2,c:10,active:0}) > db.stack.insert({a:2,b:2,c:5,active:1}) 

MONGO QUERY:

> db.stack.aggregate( ... {$match:{active:1}}, ... {$group:{_id:{a:"$a", b:"$b"}, csum:{$sum:"$c"}}}, ... {$sort:{"_id.a":1}}) 

RESULT:

{"result" : [     {"_id" : {"a" : 1,"b" : 2},"csum" : 3},     {"_id" : {"a" : 1,"b" : 1},"csum" : 1},     {"_id" : {"a" : 2,"b" : 2},"csum" : 5},     {"_id" : {"a" : 2,"b" : 1},"csum" : 13} ],"ok" : 1} 

(NOTE: I reformatted the shell result a bit so it is more readable)