db.beer.aggregate( [
{ '$group' : {
'_id' : '$brewery_country',
'beers' : { '$addToSet' : '$beer_name' },
} },
{ '$unwind' : '$beers' },
{ '$group' : { '_id' : '$_id', 'count' : { '$sum' : 1 } } },
*{ '$sort' : { 'count' : -1 } }*,
] ).pretty()
{ "_id" : "England", "count" : 912 }
{ "_id" : "United States", "count" : 320 }
{ "_id" : "Belgium", "count" : 185 }
{ "_id" : "Scotland", "count" : 93 }
{ "_id" : "Germany", "count" : 80 }
{ "_id" : "Netherlands", "count" : 79 }
{ "_id" : "Norway", "count" : 60 }
{ "_id" : "Wales", "count" : 55 }
{ "_id" : "Canada", "count" : 50 }
{ "_id" : "Denmark", "count" : 31 }
{ "_id" : "Sweden", "count" : 26 }
{ "_id" : "France", "count" : 25 }
…
