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Most SQL query languages ​​include a keyword for making a field auto-increment, but in MongoDB it is a bit more complicated. In MongoDB, there is no keyword for auto-increment.

This article will show us how to insert data in MongoDB collection using auto increment feature and we will see an example related to the topic to make it easier.

Applying auto-increment functionality in MongoDB

After inserting a new document into the collection, we need to add some fields, including sequence number, ID, etc. But if we add a few simple characters to the query, we can do this automatically.

The keyword we will use for this purpose is $inc, which increments a specific data value. Let's see how to integrate it into our query.

In the following example, we will demonstrate how to use auto increment in MongoDB. To do this, first, we need to create a new collection called count to keep track of the sequence number.

Let us initialize the collection by inserting a document as shown below.

db.count.insert(
   {
      _id: "incId",
      seq: 0
   }
)

This will initialize the incrementing sequence to 0. Now, we will create a autoIncrement()function called that will increment the count collection and the value of the specified collection.

function autoIncrement(name) {
   var ret = db.count.findAndModify(
          {
            query: { _id: name },
            update: { $inc: { seq: 1 } },
            new: true
          }
   );

   return ret.seq;
}

This function will return the incremented sequence value and we can use it on our insert function by calling the function like below.

db.mycollection.insert({ sl: autoIncrement("incId"), Name: "Retro"});
db.mycollection.insert({ sl: autoIncrement("incId"), Name: "Max"});

After executing the above command, you don’t need to increment the field value manually. After inserting the document, you will get the following output in the console:

{ _id: ObjectId("6388f500054350812fa6b073"),
  sl: 1,
  Name: 'Retro' }
{ _id: ObjectId("6388f94e054350812fa6b075"),
  sl: 2,
  Name: 'Max'
}

Please note that the commands shown in this article are for MongoDB database and need to be run on the MongoDB console.