# Feature Views

This guide introduces you to the concept of feature views in Profiles and shows how to use them in your Profiles project.

## Video walkthrough

{{< youtube Prr6glFjR_c >}}

## Overview

Profiles adds a unique ID when you create a Customer360 (C360) table. But for most activation use cases, you need to use a specific ID from your data warehouse, like user_name, email, or anonymous ID. You can achieve this using SQL, the ID graph table, and the C360 table, but it is complicated and can be difficult to maintain.

Profiles can create these pivots automatically with `feature views`. They include the same [`entity_vars`]({{< ref "profiles/dev-docs/profiles-yaml/var-groups/entity-var.md" >}}) as the C360 table but with the chosen ID as the primary key.

**SQL Keyword**: `VIEW`

## Requirements

- `entity_vars` where `is_feature` is set to `true`.
- View primary ID is included in ID graph.

## Usage

Feature views (`feature_views`) are in the [`pb_project.yaml`]({{< ref "profiles/dev-docs/pb-project-yaml/" >}}) file within the `entities` block, as shown:

```yaml
name: llm_sdr_email_content_generation
schema_version: 85
connection: llm-recommend-dev
model_folders:
  - models
entities:
  - name: user
    id_stitcher: models/user_id_stitcher
    id_types:
      - user_id
      - anonymous_id**
###########################################
    feature_views:
      using_ids:
        - id: anonymous_id
          name: anonymous_id_360
###########################################
id_types:
  - name: user_id
  - name: anonymous_id
    filters:                      # Optional
      - type: exclude
        value: ""
python_requirements:              # Optional
  - profiles_mlcorelib==0.7.2
```

## Best practices

- Profiles automatically creates a feature view where the `main_id` is the primary key, called `{entity_name}_feature_view`. It is a best practice to create another `feature view` using a desired ID type as the primary key for data activation.
- All features will be included in all feature views for an entity, unless you set `is_feature` to `false` for a specific `entity_var`.
- Feature views are defined in `pb_project.yaml` for the `user/all` [cohort]({{< ref "profiles/concepts/cohort.md" >}}). For individual cohorts, they are defined in the cohort definition in `profiles.yaml`.
- [`Cohorts`]({{< ref "profiles/concepts/cohort.md" >}}) inherit the features from their parent, so you do not need to define them at the cohort level.

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