> ## Documentation Index
> Fetch the complete documentation index at: https://docs.quickblox.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Relations

> It is possible to create a relation between objects of two different classes via `_parent_id` field.

For example, we have the class **Rating** that contains `score`, `review`, and `comment` fields. We also have a **Movie** class. So we can create a record of class **Rating** that will point to the record of the class **Movie** via its `_parent_id` field, so the `_parent_id` field will contain the ID of record from class **Movie**.

<Warning>
  This is not a simple soft link. This is actually a **hard link**. When you delete the **Movie** class record then all its children (records of class **Rating** with `_parent_id` field set to the **Movie** class record ID) will be automatically **deleted** as well.

  See [this request](/reference/create-child-record) to learn how to create a child custom record.
</Warning>

<Info>
  If you need to retrieve all children, you can retrieve records with the filter `_parent_id=<id_of_parent_class_record>`.
</Info>