mysql - how to get projections in mongodb with group operator -

i have table columns column1 & column2 looks this

    colum1 column2             1            2            3      b       2      b       4      b       6 

if perform following sql in mysql

      select column1, column2, count(*) table group column1; 

result

  column1 column2 count(*)            1         3    b         2         3 

i want execute similar query on mongodb

i tried

 query1: db.table.aggregate({$group: {_id:"$column1", count:{$sum:1}} })  query2: db.table.aggregate({$project: {column1:1, column2:1}}, {$group: {_id:"$column1", count:{$sum:1}} }) 

however result query2 same query1, seems can not populate fields other mentioned in $group column.

is there way populate other fields in mongodb along $group operator ?

i'm not sure read mysql query correctly, , don't understand why particularly useful, $first seems accomplish same thing.

however, mentioned in $first documentation, outcome depends on sorting should include sorting criterion.

data (column names shortened brevity)

> db.foo.insert({"c1" : "a", "c2" : 1}); > db.foo.insert({"c1" : "a", "c2" : 2}); > db.foo.insert({"c1" : "a", "c2" : 3}); > db.foo.insert({"c1" : "b", "c2" : 2}); > db.foo.insert({"c1" : "b", "c2" : 4}); > db.foo.insert({"c1" : "b", "c2" : 6}); 

aggregation query

> db.foo.aggregate({$group: {_id:"$c1", c2: { $first: "$c2" }, count:{$sum:1}} }) 

results

{         "result" : [                 {                         "_id" : "b",                         "c2" : 2,                         "count" : 3                 },                 {                         "_id" : "a",                         "c2" : 1,                         "count" : 3                 }         ],         "ok" : 1 }