Deleting Duplicates in MongoDB

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Deleting Duplicates in MongoDB

Author：JIYIK Last Updated：2025/04/28 Views：

If you are a database administrator, you are probably familiar with duplicate entries. Duplicate entries are a common problem in database management.

In this article, we will see how to remove duplicate entries in MongoDB, and we will also see an example with proper explanation to make the topic easier to understand.

Remove duplicate documents from a collection in MongoDB

We need to divide the task into two parts to remove duplicate entries from the database. First, we need to sort the documents in the collection according to a specific criteria, and then, we need to define a function for each document using the forEach() method.

Inside the function, we need to use a remove()method called which will remove duplicate documents. Now let's look at an example to illustrate this.

In the following example, we will demonstrate how to remove duplicate entries from our collection. Before we start, let's intentionally create some duplicate documents as follows:

{
  "sl": 1,
  "Name": "Alex"
}
{
  "sl": 1,
  "Name": "Alex"
}

Now we will execute the following command in the MongoDB console:

db.mycolletion.find({}, {
  "sl": 1
}).sort({
  _id: 1
}).forEach(function (record) {
  db.mycolletion.remove({
    _id: {
      $gt: record._id
    },
    "sl": record.sl
  });
});

We have already described the working mechanism of the above command in the introduction section. On successful execution of the command, you will get the following output in the console window.

{
  "sl": 1,
  "Name": "Alex"
}

Remember, if you are not in the target database, you will need to switch to your database. To do this, use the following command:

use Your_DB

Please note that the commands shown in this article are for MongoDB database and need to be run on the MongoDB console.

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