sql - How to do nested select in MongoDB -

how one, in mongodb, implement following sql statement?

select count(*),t1.a,t1.b    t1, t2  (t1.id = t2.t1_id)  ,   (t2.t1_id in (select id                     t1                     order id desc                     limit 10))  group 2,3  order 1 desc 

i figured out how except nested select.

i'm running outer select in loop using "$in" each value of nested select. java code follows:

basicdblist t1list = new basicdblist(); dbobject inclause = new basicdbobject("$in", t1list); dbobject t2query = new basicdbobject("t1s", inclause); dbobject nextt2;  (int query = 0; query < 10; query++) {     system.out.printf("running query %d - ", query);     dbcursor top_ten_t1s = t1coll.find().sort(new basicdbobject("v", -1)).limit(10);     while (top_ten_t1s.hasnext())     {         nextt2 = top_ten_t1s.next();         t1list.clear();         t1list.add(new long(nextt2.get("_id").tostring()));         int thecount = t2coll.find(t2query).count();     } } 

you can't in 1 query in mongodb. you'll need read result of inner query memory first (which sounds you're doing):

var ids = t1.find().sort( { _id: -1 } ).limit(10); 

and apply result outer query.