How do I insert a record from one Mongo database into another?

To insert records from one MongoDB database into another, use the find() method to retrieve documents from the source collection, then iterate through them with forEach() to insert into the destination database.

Syntax

var documents = db.sourceCollection.find();
use targetDatabase;
documents.forEach(function(doc) {
    db.targetCollection.insertOne(doc);
});

Sample Data

Let's create a collection in the "test" database with some sample documents:

db.insertOneRecordDemo.insertMany([
    {"UserName": "Larry", "UserAge": 23},
    {"UserName": "Chris", "UserAge": 26},
    {"UserName": "David", "UserAge": 25}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c9534de16f542d757e2b452"),
        ObjectId("5c9534e816f542d757e2b453"),
        ObjectId("5c9534f116f542d757e2b454")
    ]
}

Method 1: Copy All Documents

First, verify the source data:

db.insertOneRecordDemo.find().pretty();

{
    "_id": ObjectId("5c9534de16f542d757e2b452"),
    "UserName": "Larry",
    "UserAge": 23
}
{
    "_id": ObjectId("5c9534e816f542d757e2b453"),
    "UserName": "Chris",
    "UserAge": 26
}
{
    "_id": ObjectId("5c9534f116f542d757e2b454"),
    "UserName": "David",
    "UserAge": 25
}

Now copy all documents to the "sample" database:

var AllDocumentsFromSourceCollection = db.insertOneRecordDemo.find();
use sample;
AllDocumentsFromSourceCollection.forEach(function(allRecords){
    db.getAllRecordsFromSourceCollectionDemo.insertOne(allRecords);
});

Verify Results

Check if records were successfully inserted in the target database:

db.getAllRecordsFromSourceCollectionDemo.find().pretty();

{
    "_id": ObjectId("5c9534de16f542d757e2b452"),
    "UserName": "Larry",
    "UserAge": 23
}
{
    "_id": ObjectId("5c9534e816f542d757e2b453"),
    "UserName": "Chris",
    "UserAge": 26
}
{
    "_id": ObjectId("5c9534f116f542d757e2b454"),
    "UserName": "David",
    "UserAge": 25
}

Verify the collection exists in the target database:

show collections;

getAllRecordsFromSourceCollectionDemo

Key Points

• Use find() to retrieve all documents from the source collection
• forEach() iterates through each document for insertion
• Original _id values are preserved during the copy process
• Use use databaseName to switch between databases

Conclusion

The forEach() method combined with find() provides a simple way to copy documents between MongoDB databases. This approach preserves document structure and IDs while transferring data to the target collection.