How to make nested queries in MongoDb that works like nested Sql select queries

Question

I want to make an efficient query in MongoDb to find all users who have their userids listed in a usergroup. Ideally I want to make this as a single request to Mongodb. What I w

Answer 1

-sUReN

SQL Query: (group by & count of distinct)

select city,count(distinct(emailId)) from TransactionDetails group by city;

Equivalent mongo query would look like this:

db.TransactionDetails.aggregate([ 
{$group:{_id:{"CITY" : "$cityName"},uniqueCount: {$addToSet: "$emailId"}}},
{$project:{"CITY":1,uniqueCustomerCount:{$size:"$uniqueCount"}} } 
]);