MongoDB - Projection

In MongoDB, projection means selecting only the necessary data rather than selecting whole of the data of a document. If a document has 5 fields and you need to show only 3, then select only 3 fields from them.

The find() Method

MongoDB s find() method, explained in MongoDB Query Document accepts second optional parameter that is pst of fields that you want to retrieve. In MongoDB, when you execute find() method, then it displays all fields of a document. To pmit this, you need to set a pst of fields with value 1 or 0. 1 is used to show the field while 0 is used to hide the fields.

Syntax

The basic syntax of find() method with projection is as follows −

>db.COLLECTION_NAME.find({},{KEY:1})

Example

Consider the collection mycol has the following data −

{_id : ObjectId("507f191e810c19729de860e1"), title: "MongoDB Overview"},
{_id : ObjectId("507f191e810c19729de860e2"), title: "NoSQL Overview"},
{_id : ObjectId("507f191e810c19729de860e3"), title: "Tutorials Point Overview"}

Following example will display the title of the document while querying the document.

>db.mycol.find({},{"title":1,_id:0})
{"title":"MongoDB Overview"}
{"title":"NoSQL Overview"}
{"title":"Tutorials Point Overview"}
>

Please note _id field is always displayed while executing find() method, if you don t want this field, then you need to set it as 0.