How to prepend string to entire column in MongoDB?

Prepend string to entire column in MongoDB using aggregate framework. Let us first create a collection with documents −

> db.prependDemo.insertOne({"StudentFirstName":"John"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ccf3bcedceb9a92e6aa1955")
}
> db.prependDemo.insertOne({"StudentFirstName":"Chris"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ccf3bd3dceb9a92e6aa1956")
}
> db.prependDemo.insertOne({"StudentFirstName":"Robert"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ccf3bd8dceb9a92e6aa1957")
}

Following is the query to display all documents from a collection with the help of find() method −

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

This will produce the following output −

{ "_id" : ObjectId("5ccf3bcedceb9a92e6aa1955"), "StudentFirstName" : "John" }
{
   "_id" : ObjectId("5ccf3bd3dceb9a92e6aa1956"),
   "StudentFirstName" : "Chris"
}
{
   "_id" : ObjectId("5ccf3bd8dceb9a92e6aa1957"),
   "StudentFirstName" : "Robert"
}

Here is the query to prepend string to entire column in MongoDB −

> db.prependDemo.aggregate([{
...    $project: {
...       "StudentFirstName": {
...          $concat: ["Mr.", "$StudentFirstName"]
...       }
...    }
... }]);

This will produce the following output −

{ "_id" : ObjectId("5ccf3bcedceb9a92e6aa1955"), "StudentFirstName" : "Mr.John" }
{ "_id" : ObjectId("5ccf3bd3dceb9a92e6aa1956"), "StudentFirstName" : "Mr.Chris" }
{ "_id" : ObjectId("5ccf3bd8dceb9a92e6aa1957"), "StudentFirstName" : "Mr.Robert" }

Nishtha Thakur

Updated on: 2019-07-30T22:30:26+05:30

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