Delete operations in MongoDB allow you to remove documents from a collection. These operations are crucial for managing and maintaining the integrity of your data by enabling you to remove outdated, irrelevant, or incorrect data.

MongoDB provides several methods for deleting documents:

• deleteOne()
• deleteMany()
• remove().

Understanding these methods and how to use them effectively is essential for efficient data management in MongoDB.

deleteOne() Method

The deleteOne() method is used to delete a single document that matches the specified filter. If multiple documents match the filter, only the first one encountered is deleted. This method is part of MongoDB's new CRUD API introduced in version 3.2 and is designed for precise control over single-document deletions.

Syntax

db.collection.deleteOne(
  <filter>,
  <options>
)

• filter: Specifies the criteria to select the document to delete.
• options (optional): An object specifying options for the delete operation.

Examples

1. Delete a Document by a Specific Field

   db.users.deleteOne({ name: "Alice" })

   This command deletes the first document where the name is "Alice".

2. Delete a Document by ID

   db.users.deleteOne({ _id: ObjectId("507f1f77bcf86cd799439011") })

   This command deletes the document with the specified _id.

deleteMany() Method

The deleteMany() method is used to delete all documents that match the specified filter. This method is efficient for bulk deletions and ensures that all matching documents are removed from the collection.

Syntax

db.collection.deleteMany(
  <filter>,
  <options>
)

• filter: Specifies the criteria to select the documents to delete.
• options (optional): An object specifying options for the delete operation.

Examples

1. Delete Multiple Documents by a Specific Field

   db.users.deleteMany({ age: { $lt: 30 } })

   This command deletes all documents where the age field is less than 30.

2. Delete Multiple Documents by a Nested Field

   db.users.deleteMany({ "address.city": "Old City" })

   This command deletes all documents where the city field of the address object is "Old City".

remove() Method

The remove() method is an older method used to delete documents from a collection. It can delete either a single document or multiple documents depending on the justOne option. While still supported, it has been largely replaced by deleteOne() and deleteMany() in modern applications.

Syntax

db.collection.remove(
  <filter>,
  <options>
)

• filter: Specifies the criteria to select the documents to delete.
• options (optional): An object specifying options for the remove operation.

Examples

1. Delete a Single Document

   db.users.remove({ name: "Alice" }, { justOne: true })

   This command deletes the first document where the name is "Alice".

2. Delete Multiple Documents

   db.users.remove({ age: { $gte: 30 } })

   This command deletes all documents where the age field is greater than or equal to 30.