[{"_id":1,"banks":[{"name":"ABC","amt":0},{"name":"PQR","amt":-1},{"name":"XYZ","amt":3400}]},{"_id":2,"banks":[{"name":"ABC","amt":-2},{"name":"PQR","amt":2344},{"name":"XYZ","amt":7600}]}]

db.collection.aggregate([{"$unwind":"$banks"},{"$project":{"greaterThanZero":{"$cond":[{"$gt":["$banks.amt",0]},1,0]},"lessThanEqualToZero":{"$cond":[{"$lte":["$banks.amt",0]},1,0]}}},{"$group":{"_id":"$_id","greaterThanZero":{"$sum":"$greaterThanZero"},"lessThanEqualToZero":{"$sum":"$lessThanEqualToZero"}}}])