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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.
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