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How to merge array of documents in Mongo DB?
To merge, use aggregate() along with $PUSH. Let us create a collection with documents −
> db.demo64.insertOne({"Subjects":["MySQL","MongoDB","Java"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e28762bcfb11e5c34d89936")
}
> db.demo64.insertOne({"Subjects":["Oracle","Spring","Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e28763fcfb11e5c34d89937")
}Display all documents from a collection with the help of find() method −
> db.demo64.find();
This will produce the following output −
{ "_id" : ObjectId("5e28762bcfb11e5c34d89936"), "Subjects" : [ "MySQL", "MongoDB", "Java" ] }
{ "_id" : ObjectId("5e28763fcfb11e5c34d89937"), "Subjects" : [ "Oracle", "Spring", "Python" ] }Following is the query to merge array of document in MongoDB −
> db.demo64.aggregate([
... { "$group": {
... "_id": null,
... "Subjects": { "$push": "$Subjects" }
... }},
... { "$project": { "_id": 0 }}
... ]);This will produce the following output −
{ "Subjects" : [ [ "MySQL", "MongoDB", "Java" ], [ "Oracle", "Spring", "Python" ] ] }
Updated on: 30-Mar-2020
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