# Update MongoDB field using value of another field

Technology CommunityCategory: MongoDBUpdate MongoDB field using value of another field
VietMX Staff asked 1 year ago

Consider SQL command:

UPDATE Person SET Name = FirstName + ' ' + LastName

In Mongo, is it possible to update the value of a field using the value from another field?

You cannot refer to the document itself in an update (yet). You’ll need to iterate through the documents and update each document using a function like:

db.person.find().snapshot().forEach(
function (elem) {
db.person.update(
{
_id: elem._id
},
{
\$set: {
name: elem.firstname + ' ' + elem.lastname
}
}
);
}
);