MongoDB query similar to SELECT COUNT GROUP BY - mongodb

Question

My MongoDB database has the 'interviews' collection whose document structure is similar to this:
{
"_id" : ObjectId("632b97b0f2bd3f64bbc30ec8"),
"agency" : "AG1",
"year" : "2022",
"month" : "9",
"residents" : [
{
"sequential" : 1,
"name" : "Resident 1",
"statusResident" : "pending",
},
{
"sequential" : 2,
"name" : "Resident 2",
"statusResident" : "not analyzed"
},
{
"sequential" : 3,
"name" : "Resident 3",
"statusResident" : "not analyzed"
},
{
"sequential" : 4,
"name" : "Resident 4",
"statusResident" : "finished"
}
]
}
{
"_id" : ObjectId("882b99b0f2bd3f64xxc30ec8"),
"agency" : "AG2",
"year" : "2022",
"month" : "9",
"residents" : [
{
"sequential" : 1,
"name" : "Resident 10",
"statusResident" : "pending",
},
{
"sequential" : 2,
"name" : "Resident 20",
"statusResident" : "not analyzed"
}
]
}
I would like to make a query that returns something similar to SQL SELECT agency, statusResident, COUNT(*) FROM interviews GROUP BY agency, statusResident.
For these documents above, that would return something like
AG1 pending 1
AG1 not analyzed 2
AG1 finished 1
AG2 pending 1
AG2 not analyzed 1
I ran the following queries but they didn't return what I need:
db.interviews.aggregate([
{ $group: { _id: { agency: "$agency", statusResident: "$residents.statusResident", total: { $sum: "$residents.statusResident" } } } },
{ $sort: { agency: 1 } }
db.interviews.group({
key:{agency:1, "residents.statusResident":1},
cond:{year:2022},
reduce:function(current, result)
{
result.total += 1;
},
initial:{total:0}
})
I've consulted post "MongoDB SELECT COUNT GROUP BY" and "Select count group by mongodb" as well as the MongoDB documentation but to no avail. What query should I run to get a result similar to the one I want?

Answer 1

You can try this query:
First $unwind to deconstruct the array and can group by statusResident too.
Then $group by two values, agency and statusResident.
And the last stage is $project to get an easier to read output.
db.collection.aggregate([
{
"$unwind": "$residents"
},
{
"$group": {
"_id": {
"agency": "$agency",
"statusResident": "$residents.statusResident"
},
"total": {
"$sum": 1
}
}
},
{
"$project": {
"_id": 0,
"agency": "$_id.agency",
"statusResident": "$_id.statusResident",
"total": 1
}
}
])
Example here

Answer 2

Try this one
db.collection.aggregate([
{ $unwind: "$residents" },
{
$group: {
_id: {
agency: "$agency",
statusResident: "$residents.statusResident",
total: { $sum: 1 }
}
}
},
{ $sort: { agency: 1 } }
])
Mongo Playground