How to delete array elements by index in MongoDB?

You can delete array elements by index using the following two steps -

The first step is as follows -

db.yourCollectionName.update({}, {$unset : {"yourArrayFieldName.yourIndexValue" : 1 }});

The above syntax will be in "yourIndexValue" Place a null value at the position. After that you need to extract null values ​​from array field to remove from array elements.

The second step is as follows -

db.yourCollectionName.update({}, {$pull : {"yourArrayFieldName" : null}});

To implement the syntax, let us create a collection with documents. The query to create a collection using documents is as follows -

> db.removeArrayElementByItsIndexDemo.insertOne({"InstructorName":"David",
   "InstructorAge":28,"InstructorSubject":["MongoDB","MySQL","Java","SQL Server","PL/SQL"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8abbfc6cea1f28b7aa0803")
}

Display all the documents in the collection with the help of find() method. The query is as follows -

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

The following is the output -

{
   "_id" : ObjectId("5c8abbfc6cea1f28b7aa0803"),
   "InstructorName" : "David",
   "InstructorAge" : 28,
   "InstructorSubject" : [
      "MongoDB",
      "MySQL",
      "Java",
      "SQL Server",
      "PL/SQL"
   ]
}

This is the query to delete array elements by index.

Step 1- Query as follows-

> db.removeArrayElementByItsIndexDemo.update({}, {$unset : {"InstructorSubject.2" : 1 }});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Step 2-Query as follows-

> db.removeArrayElementByItsIndexDemo.update({}, {$pull : {"InstructorSubject" : null}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Let’s check Whether the array element "Java" has been deleted. The query is as follows -

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

The following is the output -

{
   "_id" : ObjectId("5c8abbfc6cea1f28b7aa0803"),
   "InstructorName" : "David",
   "InstructorAge" : 28,
   "InstructorSubject" : [
      "MongoDB",
      "MySQL",
      "SQL Server",
      "PL/SQL"
   ]
}

View the sample output, the array element "Java" has been completely deleted.

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