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$Addtoset Operator In Mongodb

In this article, we will discuss the $addToSet operator in MongoDB.

Purpose

The $addToSet operator is used within an update operation to add elements to an array field only if they do not already exist in the array.

db.collection.update(
   { [query] },
   { $addToSet: { [field]: [value] } }
)

Consider the following collection: -

To add an element, we will use the following query: -

db.mycollection.updateOne(
   { "_id": 1 },
   { $addToSet: { "interests": "sports" } }
)

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