Find Total based on group by of two mongo field - mongodb

Question

i have collection data like this -
{
"user_id" : "1",
"branch_id" : "1",
"total" : 100,
},
{
"user_id" : "1",
"branch_id" : "1",
"total" : 200
},
{
"user_id" : "1",
"branch_id" : "3",
"total" : 1400
},
{
"user_id" : "2",
"branch_id" : "1",
"total" : 100
},
{
"user_id" : "2",
"branch_id" : "1",
"total" : 100
},
I am looking to get output in the below format -
[
{
"user_id":"1",
"branch_id":"1",
"grand_total":"300"
},
{
"user_id":"1",
"branch_id":"3",
"grand_total":"1400"
},
{
"user_id":"2",
"branch_id":"1",
"grand_total":"200"
}
]
I have tried a mongo aggregate query, but the query gives output as undefined.
Basically I need to get per user wise per branch wise the total points he has earned.
Here is what I have tried but not working -
Collection.aggregate(
{
"$group": {
"_id": "$user_id",
"nameCount": { "$sum": 1 },
"branch_id": {
"$sum": {
"$cond": [ {"$branch_id":{"$ne":null}} ]
}
}
}
},
{
"$project": {
"_id": 0,
"name": "$_id",
"nameCount": 1,
"branch_id":1
}
}
);
Please help.

Answer 1

Your aggregation pipeline has to look like this:
{
"$group": {
"_id": {
user_id: "$user_id",
branch_id: "$branch_id"
},
"grand_total": {
"$sum": "$total"
},
}
}, {
"$project": {
"_id": 0,
"user_id": "$_id.user_id",
"branch_id": "$_id.branch_id",
"total": "$grand_total"
}
}
Inside your _id field in your "$group" pipeline you add the fields that you want to group your documents by. If you only want to group by one field you can write it as follows:
{"$group": {
"_id": "$user_id"
}
}
If you have multiple fields you want to group by (like it seems in your case) then you write it as follows:
{"$group": {
"_id": {
user_id: "$user_id",
branch_id: "$branch_id"
}
}
}
Every aggregation pipeline changes your document. So, in your $group if you call the sum of all totals like that "grand_total"
"grand_total": {
"$sum": "$total"
}
then in your $project pipeline that field total doesn't exist anymore. But instead we created a new field (grand_total) that is the sum.