Convert ObjectId to String in the MongoDB

Question

I have an aggregate query.

{ "$addFields": { "collegeID": (('$collegeDetail._id')), }}

where, I want to add a new field 'CollegeID' as a string version of the ObjectId stored in collegeDetail._id.

Any help will be appreciated. Thanks.

This is not currently supported, but will be available in an upcoming release. See here. — Kirk Larkin
– Kirk Larkin, Commented May 30, 2018 at 17:03
I can't see anything out there - all solutions talk of doing it in the JavaScript context, outside of an aggregation pipeline, which I guess is not what you are looking for. — Kirk Larkin
– Kirk Larkin, Commented May 30, 2018 at 17:07

Ashh · Accepted Answer · 2018-12-09 08:44:10Z

You should try $toString aggregation to convert ObjectId to string

db.strcoll.aggregate([ { "$addFields": { "collegeID": { "$toString": "$collegeDetail._id" } }} ])

iatsi · Accepted Answer · 2018-07-18 12:33:13Z

Edit: Starting from (Version 4.0 of MongoDB) Gladly MongoDB has made and update and got us a new operator that does this job.

$convert

This can be used to change the data type of value from almost each type to each type

Hope this helps;

Syed Ahsan Ali · Accepted Answer · 2018-10-25 01:43:23Z

1

The Link below will provide you javascript way to convert objectId to string: Convert ObjectID (Mongodb) to String in JavaScript

answered May 30, 2018 at 17:04

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1 Comment

Thanks for the help, but as you see in the question I wanted to do it in the query itself.