How to update and insert new element in array in MongoDB

Question

I am new to MongoDB. I want to store User data in an array. The data is single unique document.lets say the document is like this.

User { id: number, name: string }

{
  _id : 001,
  room: User[],
}

I want to do something this...

push element (User) if room[] doesn't have it.
update User data.

Like there is upsert option in update operation.

  DB.Collection.updateOne(
      { _id: "001" },
      { $set: { name: "Bar" } },
      { upsert: true }
    );

How can I do something like this,In an Array of a Document?

Nur · Accepted Answer · 2020-09-14 09:23:50Z

5

+50

You can use $set operation to update Embedded Document with $(update) or $[$[<identifier>].But It's not work good with upsert So in order insert new Document use $push.Do something to update data or append data separately.

// push element (User) if room[] doesn't have it.

DB.Collection.updateOne(
    { "room.id": { $ne: "001" } },
    { $push: { "room": { id: "001", name: "Bar" } } },
);

// update User data

DB.Collection.updateOne(
    { "room.id": "001"  },
    { $set { "room.$": { id: "001", name: "Foo" } } },
);

edited Sep 14, 2020 at 9:23

answered Sep 14, 2020 at 9:16

Nur

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Mallik · Accepted Answer · 2020-09-13 13:20:40Z

//you can use update with $set or $push based on whether you want to update one element in array with override/update or push another element.
> db.rooms.find();
{ "_id" : 1, "room" : [ "raj" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2, "room" : [ "raj" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3, "room" : [ "raj" ] }
> db.rooms.updateMany(   {},   {$set:{"room":["john"]}} );
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 3 }
> db.rooms.find();
{ "_id" : 1, "room" : [ "john" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2, "room" : [ "john" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3, "room" : [ "john" ] }
> db.rooms.updateMany(   {},   {$push:{"room":["mike"]}} );
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 3 }
> db.rooms.find();
{ "_id" : 1, "room" : [ "john", [ "mike" ] ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2, "room" : [ "john", [ "mike" ] ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3, "room" : [ "john", [ "mike" ] ] }
> db.rooms.updateMany(   {},   {$push:{"room":"mike"}} );
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 3 }
> db.rooms.find();
{ "_id" : 1, "room" : [ "john", [ "mike" ], "mike" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2, "room" : [ "john", [ "mike" ], "mike" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3, "room" : [ "john", [ "mike" ], "mike" ] }
>

the push will add a field in the document if it does not exist, so a specific check for field room is not required.

> db.rooms.find();
{ "_id" : 1, "room" : [ "john", [ "mike" ], "mike" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2, "room" : [ "john", [ "mike" ], "mike" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3, "room" : [ "john", [ "mike" ], "mike" ] }
> db.rooms.updateMany(
...   {},
...   {$unset:{"user":""}}
... );
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 0 }
> db.rooms.updateMany(   {},   {$unset:{"room":""}} );
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 3 }
> db.rooms.find();
{ "_id" : 1 }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2 }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3 }
> db.rooms.updateMany(   {},   {$push:{"room":"mike"}} );
{ "acknowledged" : true, "matchedCount" : 3, "modifiedCount" : 3 }
> db.rooms.find();
{ "_id" : 1, "room" : [ "mike" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff51"), "id" : 2, "room" : [ "mike" ] }
{ "_id" : ObjectId("5f5e10f2598d922a1e6eff52"), "id" : 3, "room" : [ "mike" ] }
>

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