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MongoDB query to get only specific fields in nested array documents?
To get only specific fields in nested array documents, use $filter along with $project. Let us create a collection with documents −
> db.demo342.insertOne({
... "Id": "101",
... "details1" : {
... "details2" : [
... {
... "details3" : [
... {
... "Name": "Mike",
... "CountryName" : "US"
... },
... {
... "Name": "David",
... "CountryName" : "AUS"
... },
... {
... "Name": "Bob",
... "CountryName" : "UK"
... }
... ]
... }
... ]
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e53ef99f8647eb59e5620a9")
}Display all documents from a collection with the help of find() method −
> db.demo342.find();
This will produce the following output −
{ "_id" : ObjectId("5e53ef99f8647eb59e5620a9"), "Id" : "101", "details1" : { "details2" : [ { "details3" : [ { "Name" : "Mike", "CountryName" : "US" }, { "Name" : "David", "CountryName" : "AUS" }, { "Name" : "Bob", "CountryName" : "UK" } ] } ] } }Following is the query to get only specific fields in nested array documents −
> db.demo342.aggregate([
... { "$project": {
... "details1": {
... "details2": {
... "$filter": {
... "input": {
... "$map": {
... "input": "$details1.details2",
... "in": {
... "details3": {
... "$filter": {
... "input": "$$this.details3",
... "cond": { "$eq": ["$$this.Name", "Bob"] }
... }
... }
... }
... }
... },
... "cond": { "$ne": ["$$this.details3", []] }
... }
... }
... }
... }}
... ])This will produce the following output −
{ "_id" : ObjectId("5e53ef99f8647eb59e5620a9"), "details1" : { "details2" : [ { "details3" : [ { "Name" : "Bob", "CountryName" : "UK" } ] } ] } }
Updated on: 02-Apr-2020
660 Views
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