How do I remove duplicates in MongoDB?

How do I remove duplicates in MongoDB?

1. Duplicate records can be removed from a MongoDB collection by creating a unique index on the collection and specifying the dropDups option.
2. Assuming the collection includes a field named record_id that uniquely identifies a record in the collection, the command to use to create a unique index and drop duplicates is:

How do I get unique records in MongoDB?

To get unique values and ignore duplicates, use distinct() in MongoDB. The distinct() finds the distinct values for a specified field across a single collection and returns the results in an array.

What is $in in MongoDB?

The $in operator selects the documents where the value of a field equals any value in the specified array. To specify an $in expression, use the following prototype: For comparison of different BSON type values, see the specified BSON comparison order.

What is $project in MongoDB?

The $project takes a document that can specify the inclusion of fields, the suppression of the _id field, the addition of new fields, and the resetting of the values of existing fields. Adds a new field or resets the value of an existing field. Changed in version 3.6: MongoDB 3.6 adds the variable REMOVE .

How does MongoDB prevent duplicate records?

To insert records in MongoDB and avoid duplicates, use “unique:true”.

How do I remove duplicate errors in MongoDB?

For example, you could use aggregation as suggested on: MongoDB duplicate documents even after adding unique key. This will keep the first unique document for each source_references. key value, and drop any subsequent documents that would otherwise cause a duplicate key violation.

Does MongoDB allow duplicates?

A unique index ensures that the indexed fields do not store duplicate values; i.e. enforces uniqueness for the indexed fields. By default, MongoDB creates a unique index on the _id field during the creation of a collection.

Does MongoDB duplicate data?

If you need to manipulate documents that have more than one field with the same name, see the driver documentation for your driver. Some documents created by internal MongoDB processes may have duplicate fields, but no MongoDB process will ever add duplicate fields to an existing user document.

How do I avoid duplicate errors in MongoDB?

In MongoDB, the primary key is reserved for the _id field. This is a system field and gets created by default when inserting new records. When you want to enforce the uniqueness in other fields, you can use unique index.

How can I find duplicates in my MongoDB database?

Finding Duplicates with Aggregations You can find duplicate values within your MongoDB database using the aggregate method along with the $group and $match aggregation pipeline operators. For a closer look at MongoDB’s aggregation pipeline operators see the article Aggregations in MongoDB by Example.

How to create a document collection in MongoDB?

The query to create a collection with a document is as follows − Display all documents from a collection with the help of find () method. The query is as follows −

How to insert a CSV file in MongoDB?

To insert the CSV file, we’ll be using mongoimport to create a database called banks and a collection called list. Make sure to use the credentials for your deployment. One you’ve run mongoimport in the terminal, you should see that 559 documents have been successfully imported into your database.

Where can I find list of Duplicate names?

You can find the list of duplicate names using the following aggregate pipeline: Group all the records having similar name. Match those groups having records greater than 1. Then group again to project all the duplicate names as an array.