How to update MongoDB field using value of another field

Question

Is it possible to update a field using the value of another field?

Here is my schema

var timeSchema = new mongoose.Schema({
    hours: Number,
    minutes: Number
});

module.exports = mongoose.model("Time", timeSchema);

I want the value of minutes to be hours * 60 when minutes become 0

Here is my code

Time.updateMany({}, {minutes: hours * 60});

My code throws an error which says hours is not defined

Is there any possible way to update minutes using the value of hours?

Does this answer your question? [Update MongoDB field using value of another field](https://stackoverflow.com/questions/3974985/update-mongodb-field-using-value-of-another-field) — ambianBeing, May 11 '20 at 04:08
@JeromeBravo : What didn't work ? What have you tried & your DB version ? what do you mean by *when minutes become 0* ? — whoami - fakeFaceTrueSoul, May 11 '20 at 04:20
Code: Time.updateMany({}, {$set: {minutes: $hours * 60}}); It still says that $hours is not defined. My MongoDB version is 4.2.5 — Jerome Bravo, May 11 '20 at 04:25
@whoami I have a function that decrease the number of minutes — Jerome Bravo, May 11 '20 at 04:33
This is not a good solution, but its works db.timeCollection.find().snapshot().forEach( function (elemt) { db.timeCollection.update( { _id: elemt._id }, { $set: { minutes: elemt.hours*60 } } ); } ); — Bivin Vinod, May 11 '20 at 04:34

score 2 · Accepted Answer · answered May 11 '20 at 04:32

Starting from MongoDB version 4.2, You can execute aggregation pipeline in updates i.e; you can utilize certain aggregation stages/operators in updates. So update part will be wrapped in [].

Try below query :

Time.updateMany({}, [{$set: {minutes: {$multiply : ['$hours', 60 ]}}}])

In the above query we've used $set alias $addFields stage of aggregation & $multiply aggregation operator to multiple existing hours field with 60 & store the value in minutes field.

Note : Just in case .updateMany() throws any error try the same with .update() with { multi : true } option.

How to update MongoDB field using value of another field

1 Answers1