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How would I filter out sub documents in MongoDB?
To filter out sub documents, use MongoDB aggregate and in that, use $unwind. Let us create a collection with documents −
> db.demo662.insertOne(
... {
... "details":[
... {
... Name:"Chris",
... Marks:35
... },
... {
... Name:"Bob",
... Marks:45
... },
... {
... Name:"David",
... Marks:30
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea1b2be24113ea5458c7d04")
}Display all documents from a collection with the help of find() method −
> db.demo662.find();
This will produce the following output −
{ "_id" : ObjectId("5ea1b2be24113ea5458c7d04"), "details" : [ { "Name" : "Chris", "Marks" : 35 }, { "Name" : "Bob", "Marks" : 45 }, { "Name" : "David", "Marks" : 30 } ] }Following is the query to filter out sub documents −
> db.demo662.aggregate({$unwind:"$details"},{$match:{"details.Marks":{$gt:40}}})This will produce the following output −
{ "_id" : ObjectId("5ea1b2be24113ea5458c7d04"), "details" : { "Name" : "Bob", "Marks" : 45 } }
Updated on: 13-May-2020
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