MongoDB $push Operator

In the following examples, we are working with

Database: w3wiki
Collection: contributor
Document: two documents that contain the details of the contributor in the form of field-value pairs

Appending a single value to an array example using $push operator

In this example, we are appending a single value, i.e., “C++” to an array field, i.e., language field in the document that satisfy the condition(name: “Rohit”).

Query:

db.contributor.update({name: "Rohit"}, {$push: {language: "C++"}})

Output:

Appending multiple values to an array using $push operator

In this example, we are appending multiple values, i.e., [“C”, “Ruby”, “Go”] to an array field, i.e., language field in the document that satisfy the condition(name: “Sumit”).

Query:

db.contributor.update({name: "Sumit"}, {$push: {language: {$each: ["C", "Ruby", "Go"]}}})

Output:

Appending multiple values to an array in the nested/embedded document using $push operator:

In this example, we are appending multiple values, i.e., [89, 76.4] to an array field, i.e., personal.semesterMarks field of a nested/embedded document.

Query:

db.contributor.update({name: "Sumit"}, 
                      {$push: {"personal.semesterMarks": {$each: [89, 76.4]}}})

Output:

Using modifiers with $push operator example

In this example, we are using multiple modifiers like $each, $sort, and $slice with $push operator.

Query:

db.contributor.update({name: "Rohit"},
                      {$push: { language: { $each: ["C", "Go"],
                                $sort: 1, $slice: 4}}})

Here,

• The $each modifier is used to add multiple documents to the language array.
• The $sort modifier is used to sort all the items of the modified language array in ascending.
• The $slice modifier is used to keep only the first four sorted items of the language array.

Output:

MongoDB $push operator appends a value to the already existing array within a document.