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Find when the keys are unknown in MongoDB?
To find when the keys are unknown, use $addField and $objectToArray. Let us first create a collection with documents −
> db.demo375.insertOne(
... {
... "details":{
... "Name":"John",
... "Age":23
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5a0ae42ae06a1609a00b06")
}
> db.demo375.insertOne(
... {
... "details":{
... "Name":"David",
... "Age":21
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5a0ae42ae06a1609a00b07")
}
> db.demo375.insertOne(
... {
... "details":{
... "Name":"David",
... "Age":22
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5a0ae42ae06a1609a00b08")
}Display all documents from a collection with the help of find() method −
> db.demo375.find();
This will produce the following output −
{ "_id" : ObjectId("5e5a0ae42ae06a1609a00b06"), "details" : { "Name" : "John", "Age" : 23 } }
{ "_id" : ObjectId("5e5a0ae42ae06a1609a00b07"), "details" : { "Name" : "David", "Age" : 21 } }
{ "_id" : ObjectId("5e5a0ae42ae06a1609a00b08"), "details" : { "Name" : "David", "Age" : 22 } }Following is the query to find when the keys are unknown −
> db.demo375.aggregate([
... { "$addFields": {
... "UnknownKeys": { "$objectToArray": "$$ROOT" }
... }},
... { "$match": { "UnknownKeys.v.Name": "David" }},
... { "$project": { "UnknownKeys": 0 }}
... ])This will produce the following output −
{ "_id" : ObjectId("5e5a0ae42ae06a1609a00b07"), "details" : { "Name" : "David", "Age" : 21 } }
{ "_id" : ObjectId("5e5a0ae42ae06a1609a00b08"), "details" : { "Name" : "David", "Age" : 22 } }
Updated on: 02-Apr-2020
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