show dbs;
use testdb;
use testdb;
show collections
db.testData.insert({example: 1}}
db.mycollection.find()
db.mycollection.find({country: "UK"})
db.mycollection.find( { "price" : { "$exists" : false } } ) ref: http://docs.mongodb.org/manual/reference/operator/query/exists/#op._S_exists
db.testData.insert({example: 1}}
db.testData.update({example: 1},{ $set: {example: 1}}
db.price.aggregate([{$group: {_id: "$_id.sku_id",count: { $sum: 1 },total: {$sum: "$price.amount"}}}])