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The $set operator is used to change or add specific fields in a document without replacing the whole document.
db.collection.updateOne(
{ <filter> },
{ $set: { <field1>: <value1>, <field2>: <value2>, ... } }
)The updateOne method updates a single document matching the filter.
The $set operator only changes the specified fields and leaves others untouched.
db.users.updateOne(
{ username: "alice" },
{ $set: { email: "alice@example.com" } }
)db.products.updateOne(
{ productId: 123 },
{ $set: { price: 19.99, stock: 50 } }
)db.orders.updateOne(
{ orderId: 456 },
{ $set: { status: "shipped" } }
)This example first adds an employee named John. Then it updates John's role and active status using $set. Finally, it retrieves John's updated document.
db.employees.insertOne({ name: "John", role: "Developer", active: true })
db.employees.updateOne(
{ name: "John" },
{ $set: { role: "Senior Developer", active: false } }
)
db.employees.find({ name: "John" }).toArray()If the field does not exist, $set will add it to the document.
Using $set prevents overwriting the entire document, which can avoid accidental data loss.
$set changes or adds specific fields in a document.
It is used with update methods like updateOne or updateMany.
Only the fields inside $set are affected; others stay the same.
$set operator do in MongoDB?$set$set operator is used to update existing fields or add new fields in a MongoDB document without affecting other fields.$unset, replacing documents uses replaceOne, and creating collections is unrelated to $set.$set updates or adds fields [OK]age to 30 in a document using $set?$set syntax$set operator requires an object with field-value pairs inside curly braces: {$set: {field: value}}.$set syntax uses object with field-value pairs [OK]{ name: 'Alice', city: 'Paris' }, what will be the document after running db.users.updateOne({name: 'Alice'}, {$set: {city: 'London', age: 25}})?$set effect on fields$set operator updates existing fields and adds new fields without removing others.city changes from 'Paris' to 'London', and new field age with value 25 is added. The name field remains unchanged.$set updates and adds fields, keeps others [OK]db.products.updateOne({id: 101}, {$set: {price: 20, stock}}). What is the problem?$set operator requires each field to have a value. Here, stock is listed without a value, which is invalid syntax.employees collection to add a new field status with value 'active' only if the field status does not already exist. Which update command using $set is correct?