I have a personal project and I am new in MongoDB aggregate function. I got the correct result querying two collections using $lookup
but I want to modify the result and get my desired output.
Here is my Sample Collection
"users": [
{
"_id" : "60499e72b60a8819c4e0fa03"
"LastName": "Doe"
"FirstName" "John"
}
]
"userdocuments": [
{
"_id": "61025b9f890bacbe8f450f6a",
"userid": 60499e72b60a8819c4e0fa03,
documents: {
documentOne: {
documentTitle: "This is Document One"
},
documentTwo: {
documentTitle: "This is Document Two"
},
documentThree: {
documentTitle: "This is Document Three"
},
}
}
]
I'm getting a correct result like this using $lookup
and $unwind
https://mongoplayground.net/p/k1lmvJg-tB7
[
{
"FirstName": "John",
"LastName": "Doe",
"_id": "60499e72b60a8819c4e0fa03",
"documents": {
"_id": "61025b9f890bacbe8f450f6a",
"userid": "60499e72b60a8819c4e0fa03"
"documents": {
"documentOne": {
"documentTitle": "This is Document One"
},
"documentThree": {
"documentTitle": "This is Document Three"
},
"documentTwo": {
"documentTitle": "This is Document Two"
}
},
}
}
]
But I want my output like this. And I want to project userid
and _id
so I can get my desired output. Thanks you so much for helping
[
{
"FirstName": "John",
"LastName": "Doe",
"_id": "60499e72b60a8819c4e0fa03",
"documents": {
"documentOne": {
"documentTitle": "This is Document One"
},
"documentThree": {
"documentTitle": "This is Document Three"
},
"documentTwo": {
"documentTitle": "This is Document Two"
}
},
}
}
]
You can select first element from documents
array by $arrayElemAt
or $first
(v4.4) operators after lookup stage,
{
$addFields: {
Documents: {
$arrayElemAt: ["$Documents.documents", 0]
}
}
}
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