---
title: Null Engine reference
meta:
    description: Use the Null engine to ignore data.
---

# Null engine

When writing to a `Null` table, data is ignored. When reading from a `Null` Data Source, the response is empty.

You can use the Null engine to create a Materialized View from a `Null` table that transforms the data as it's sent to the Null Data Source so the Target Data Source will receive the transformed data and the original will be discarded.

```mermaid
graph LR
    A["non_persisted.datasource (Null)"]:::datasource --> B["transformation.pipe (Materialization)"]:::pipe
    B --> C["transformed_persisted.datasource (MergeTree)"]:::datasource

    classDef datasource fill:#bb6bd9,color:#fff
    classDef pipe fill:#fea827,color:#fff
```

Example: for masking some PII data.

```tb {% title="event.datasource" %}
SCHEMA >
    `action` LowCardinality(String) `json:$.action`,
    `timestamp` DateTime64(3) `json:$.timestamp`,
    `version` LowCardinality(String) `json:$.version`,
    `userEmail` String `json:$.userEmail` DEFAULT '',
    `workspaceId` String `json:$.workspaceId` DEFAULT '',
    `payload` String `json:$.payload`

ENGINE Null
```

```tb {% title="mask_events_mat.pipe" %}
DESCRIPTION >
    Mask events for mat view

NODE maskEvents
SQL >
    SELECT
        action, timestamp, version, cityHash64(userEmail) as userEmailMasked, workspaceId, payload
    FROM event

TYPE Materialized
DATASOURCE event_masked
```

```tb {% title="event_masked.datasource" %}
SCHEMA >
    `action` LowCardinality(String),
    `timestamp` DateTime64(3),
    `version` LowCardinality(String),
    `userEmailMasked` UInt64,
    `workspaceId` String ,
    `payload` String

ENGINE MergeTree
ENGINE_PARTITION_KEY toYear(timestamp)
ENGINE_SORTING_KEY action, workspaceId, timestamp
```