This tutorial explains the crucial difference between updating a document and replacing one in MongoDB, and shows you how to use the correct operations.

What you will learn:

The Key Difference: An Update (using updateOne, updateMany) changes specific fields in a document using operators like $set or $inc. A Replace (using replaceOne) deletes the entire document and inserts a new one in its place (while keeping the original _id).


db.collection.updateOne(): How to modify the first document that matches your query.

db.collection.updateMany(): How to modify all documents that match your query.

db.collection.replaceOne(): How to completely replace a single document.

Update Operators ($set, $inc, $unset):

$set: To change or add a field's value.

$inc: To increment or decrement a number (e.g., counters, scores).

$unset: To completely remove a field from a document.

Example (updateOne with $set and $inc): db.users.updateOne({ name: "Alice" }, { $set: { city: "Miami" }, $inc: { age: 1 } })

Example (replaceOne): db.users.replaceOne({ name: "Alice" }, { name: "Alice V2", email: "[email protected]" })

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