How to change the type of a field in MongoDB?

Let us convert string type to int for an example. Aggregation does not allow us to directly change the type of a field; therefore, you need to write a code to convert the type of a field.

At first, create a collection with document. After that we will get the type of every field. The query to create a collection with document is as follows

>db.changeDataType.insertOne({"StudentName":"Larry","StudentAge":23,"StudentZipCode":" 10001","isProgrammer":false}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c6ed4976fd07954a4890694") }

Display all documents from a collection with the help of find() method. The query is as follows:

> db.changeDataType.find().pretty();

The following is the output:

{    "_id" : ObjectId("5c6ed4976fd07954a4890694"),    "StudentName" : "Larry",    "StudentAge" : 23,    "StudentZipCode" : "10001",    "isProgrammer" : false }

Now let us check type of every field in a collection. The query is as follows to check the type of every field:

> checkType=db.changeDataType.findOne(); {    "_id" : ObjectId("5c6ed4976fd07954a4890694"),    "StudentName" : "Larry",    "StudentAge" : 23,    "StudentZipCode" : "10001",    "isProgrammer" : false }

Now here we will use the above variable “checkType” to get the type of every variable. The query is as follows:

> typeof checkType._id; object > typeof checkType.StudentName; string > typeof checkType.StudentAge; number > typeof checkType.StudentZipCode; string > typeof checkType.isProgrammer; boolean

Now, change the type of “StudentZipCode” from string to number type. The query is as follows:

> db.changeDataType.find().forEach(function(ch) ... { ... db.changeDataType.update({ ... "_id":ch._id}, ... {"$set": ... { ... "StudentZipCode":parseInt(ch.StudentZipCode) ... } ... }); ... });

I have changed the type of “StudentZipCode” from string to number type. To verify, let us follow what we saw above to check the type of field in a collection:

> againCheckType=db.changeDataType.findOne(); {    "_id" : ObjectId("5c6ed4976fd07954a4890694"),    "StudentName" : "Larry",    "StudentAge" : 23,    "StudentZipCode" : 10001,    "isProgrammer" : false }

Use the above variable to check the type of field:

> typeof againCheckType.StudentZipCode; number

Look at the above output now, the “StudentZipCode” field have been changed from String type to number.