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MongoDB: The Complete Guide

Update Documents - Part 4

Explore how to update documents in MongoDB by using advanced operators such as $position to insert elements at specific array positions, $slice to limit array size, and $sort to order array values. Understand these operations through practical examples to efficiently manage array fields in your database.

We'll cover the following...

＄position operator

We use the ＄position operator to add a value at the specific position.We can only use it with ＄each operator.

{ 
  $push: { 
    <field>: { 
      $each: [ 
        <value>, 
        ...
      ],
      $position: <numeric value>
    } 
  } 
}

The ＄position value indicates the value on the zero-based index.

  • If the ＄position = 0, it pushes the values e from the start of the array.
  • If the ＄position > 0, it pushes the values from the provided index.
  • If the ＄position < 0, it looks at the index from reverse order, then pushes the values.

First, let’s insert a task with an array field to show the use of the ＄position.

Markdown
db.tasks.insertOne({
      name: "Learn MongoDB Topic 1",
      tags: ["new", "learning", "MongoDB"]
});

Below is an example to insert tags ...