summing count result in two group - mongodb

Question

My collection's data are something like this :
[
{
ANumberAreaCode: "+98",
BNumberAreaCode: "+1",
AccountingTime: 1629754886,
Length: 123
},
{
ANumberAreaCode: "+44",
BNumberAreaCode: "+98",
AccountingTime: 1629754786,
Length: 123
},
{
ANumberAreaCode: "+98",
BNumberAreaCode: "+96",
AccountingTime: 1629754886,
Length: 998
}
]
I'm going to group on countries codes and count result (summing country codes in ANumberAreaCode and BNumberAreaCode ) .
This is my group sample :
{ "$group": {
"_id": {
"ANumberAreaCode": "$ANumberAreaCode",
},
"count": { "$sum": 1 }
}},
{ "$group": {
"_id": {
"BNumberAreaCode": "$BNumberAreaCode",
},
"count": { "$sum": 1 }
}},
now , how can i summing count result of two above queries for common countries ?
I'm looking for a query that give me this result :
+98 : 3
+44 : 1
+1 :1
+96 :1

Answer 1

You can use this aggregation pipeline:
$facet to get both group, by A and B. This creates two objects: groupA and groupB.
Then using $concatArrays into $project stage it will concat two ouputs.
Deconstructs the array using $unwind
And $group again by values using $sum to get the total.
db.collection.aggregate([
{
"$facet": {
"groupA": [
{
"$group": {
"_id": "$ANumberAreaCode",
"total": {
"$sum": 1
}
}
}
],
"groupB": [
{
"$group": {
"_id": "$BNumberAreaCode",
"total": {
"$sum": 1
}
}
}
]
}
},
{
"$project": {
"result": {
"$concatArrays": [
"$groupA",
"$groupB"
]
}
}
},
{
"$unwind": "$result"
},
{
"$group": {
"_id": "$result._id",
"total": {
"$sum": "$result.total"
}
}
}
])
Example here