Introduction to MongoDB collection.find() Method

find() is one of the most commonly used methods in MongoDB for retrieving documents from a collection. The method takes a query object as a parameter and returns a cursor pointing to the matching documents. This cursor can be used to iterate through the matching documents or retrieve a specific set of documents. The find() method returns a pointer rather than actual data, and data is only returned when the pointer is iterated.

Syntax

The syntax for the find() method is as follows:

db.collection.find(query, projection)

The query parameter is a document specifying the matching conditions, while the projection parameter is used to specify which fields to return.

Use Cases

The find() method can be used to retrieve documents from a collection that satisfy specific conditions. By passing a query object, you can specify the conditions that need to be matched. In practice, the find() method can be used to implement highly flexible queries.

Examples

Here are two examples of using the find() method:

Example 1

Suppose there is a collection named users containing the following documents:

{ "_id" : 1, "name" : "Alice", "age" : 25 }
{ "_id" : 2, "name" : "Bob", "age" : 30 }
{ "_id" : 3, "name" : "Charlie", "age" : 35 }

The following code uses the find() method to retrieve the user who is 30 years old from the users collection:

db.users.find({ age: 30 })

Executing the above code will return the following result:

{ "_id" : 2, "name" : "Bob", "age" : 30 }

Example 2

Suppose there is a collection named articles containing the following documents:

{ "_id" : 1, "title" : "Introduction to Mongodb", "category" : "Database", "author" : "Alice" }
{ "_id" : 2, "title" : "Mongodb aggregation framework", "category" : "Database", "author" : "Bob" }
{ "_id" : 3, "title" : "Mongodb performance tuning", "category" : "Database", "author" : "Charlie" }

The following code uses the find() method to retrieve the title and author of the articles belonging to the Database category and written by Bob from the articles collection:

db.articles.find(
  { category: "Database", author: "Bob" },
  { title: 1, author: 1 }
)