---
title: NOT_IMPLEMENTED ClickHouse® error
meta:
  description: Learn how to fix the NOT_IMPLEMENTED error in ClickHouse and Tinybird. Understand what causes it and see examples of how to resolve it
---

# NOT_IMPLEMENTED ClickHouse® error

{% callout %}
This error usually means you're trying to use a feature or operation that isn't implemented in ClickHouse®. This can happen when using features from other database systems or newer ClickHouse® features in older versions.
{% /callout %}

The `NOT_IMPLEMENTED` error in ClickHouse® (and Tinybird) happens when you try to use a feature, function, or operation that isn't implemented in ClickHouse® or isn't available in your version. This commonly occurs when using features from other database systems or trying to use newer ClickHouse® features in older versions.

## What causes this error

You typically see it when:

* Using features from other database systems (MySQL, PostgreSQL, etc.)
* Using newer ClickHouse® features in older versions
* Using unsupported SQL operations
* Using client-specific features that aren't implemented
* Using deprecated or removed features

## Example errors

```sql {% title="Fails: MySQL-specific feature" %}
SELECT * FROM events FOR UPDATE
```

```sql {% title="Fails: PostgreSQL-specific feature" %}
SELECT * FROM events OFFSET 10 ROWS FETCH NEXT 5 ROWS ONLY
```

```sql {% title="Fails: unsupported operation" %}
UPDATE events SET event_type = 'click' WHERE user_id = 123
```

{% callout type="caution" %}
ClickHouse® has no general-purpose UPDATE or DELETE. Only lightweight updates/deletes are available on MergeTree tables with `allow_experimental_lightweight_delete=1` or `allow_experimental_lightweight_update=1`.
{% /callout %}

```sql {% title="Fails: newer ClickHouse feature" %}
SELECT * FROM events USING SAMPLE 0.1
```

## How to fix it

### Use ClickHouse®-compatible syntax

Replace unsupported features with ClickHouse® equivalents:

```sql {% title="Fix: use ClickHouse pagination" %}
SELECT * FROM events LIMIT 5 OFFSET 10
```

### Use supported operations

Replace unsupported operations with supported alternatives:

```sql {% title="Fix: use INSERT for updates" %}
INSERT INTO events_new SELECT * FROM events WHERE user_id != 123
INSERT INTO events_new (user_id, event_type) VALUES (123, 'click')
```

### Check ClickHouse® version

Verify feature support in your ClickHouse® version:

```sql {% title="Check ClickHouse version" %}
SELECT version()
```

### Use alternative approaches

Find alternative ways to achieve the same result:

```sql {% title="Fix: use alternative approach" %}
SELECT * FROM events SAMPLE 0.1
```

## Common patterns and solutions

### Pagination

ClickHouse® pagination syntax:

```sql {% title="Correct pagination" %}
SELECT * FROM events ORDER BY timestamp DESC LIMIT 10 OFFSET 20
```

### Data modification

ClickHouse® doesn't support UPDATE/DELETE like other databases:

```sql {% title="Alternative to UPDATE" %}
-- Use INSERT with deduplication
INSERT INTO events_new SELECT * FROM events WHERE user_id != 123
INSERT INTO events_new (user_id, event_type) VALUES (123, 'click')
```

### Using MergeTree engines for "updates"

```sql {% title="ReplacingMergeTree for updates" %}
CREATE TABLE events_replacing (
    user_id UInt32,
    event_type String,
    timestamp DateTime
) ENGINE = ReplacingMergeTree() ORDER BY user_id

-- Insert new row to "update"
INSERT INTO events_replacing VALUES (123, 'click', now())
```

{% callout type="tip" %}
Use `CollapsingMergeTree` or `ReplacingMergeTree` for "update by inserting new rows" patterns.
{% /callout %}

### Sampling

ClickHouse® sampling syntax:

```sql {% title="Correct sampling" %}
SELECT * FROM events SAMPLE 0.1
SELECT * FROM events SAMPLE 1000 ROWS
```

### Transactions

ClickHouse® has limited transaction support:

```sql {% title="ClickHouse transaction approach" %}
-- Use atomic operations where possible
-- Consider using Materialized Views for complex updates
```

## Advanced solutions

### Using Materialized Views

For complex data modifications:

```sql {% title="Materialized View for updates" %}
CREATE MATERIALIZED VIEW events_updated AS
SELECT
    user_id,
    CASE WHEN user_id = 123 THEN 'click' ELSE event_type END as event_type,
    timestamp
FROM events
```

### Using INSERT with deduplication

For data replacement:

```sql {% title="INSERT with deduplication" %}
INSERT INTO events_new
SELECT
    user_id,
    CASE WHEN user_id = 123 THEN 'click' ELSE event_type END as event_type,
    timestamp
FROM events
```

### Using window functions

For complex aggregations:

```sql {% title="Window functions for complex logic" %}
SELECT
    user_id,
    event_type,
    ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY timestamp) as row_num
FROM events
```

{% callout type="tip" %}
Using `WITH TOTALS` or settings `allow_experimental_window_functions = 1` may be required for window functions.
{% /callout %}

## ClickHouse®-specific features

### Using ReplacingMergeTree

For handling updates:

```sql {% title="ReplacingMergeTree example" %}
CREATE TABLE events_replacing (
    user_id UInt32,
    event_type String,
    timestamp DateTime,
    version UInt32
) ENGINE = ReplacingMergeTree(version)
ORDER BY (user_id, timestamp)
```

### Using CollapsingMergeTree

For handling deletes:

```sql {% title="CollapsingMergeTree example" %}
CREATE TABLE events_collapsing (
    user_id UInt32,
    event_type String,
    timestamp DateTime,
    sign Int8
) ENGINE = CollapsingMergeTree(sign)
ORDER BY (user_id, timestamp)
```

## Feature compatibility

### MySQL to ClickHouse®

| MySQL Feature | ClickHouse® Alternative | Description |
|---------------|----------------------|-------------|
| `FOR UPDATE` | Not supported | Use appropriate table engines |
| `LIMIT x,y` | `LIMIT y OFFSET x` | Pagination syntax |
| `UPDATE` | `INSERT` with deduplication | Data modification |
| `DELETE` | `INSERT` with sign column | Data deletion |

### PostgreSQL to ClickHouse®

| PostgreSQL Feature | ClickHouse® Alternative | Description |
|-------------------|----------------------|-------------|
| `OFFSET x ROWS FETCH NEXT y ROWS` | `LIMIT y OFFSET x` | Pagination syntax |
| `JSONB` | `String` with JSON functions | JSON handling |
| `UPDATE` | `INSERT` with deduplication | Data modification |
| `RETURNING` | Not supported | Use separate SELECT |

## Tinybird-specific notes

In Tinybird, this error often occurs when:

* Using unsupported ClickHouse® features in Pipes
* Trying to use features not available in Tinybird's ClickHouse® version
* Using client-specific methods that aren't supported
* Working with Materialized Views that use unsupported operations

To debug in Tinybird:

1. Check Tinybird's ClickHouse® version and supported features
2. Use the Query Builder to test operations
3. Consult Tinybird documentation for supported features
4. Use alternative approaches for unsupported operations

## Best practices

### Feature compatibility

* Check ClickHouse® documentation before using new features
* Test operations in development environment first
* Use version-specific feature checks
* Keep up with ClickHouse® updates and changes

### Alternative approaches

* Use Materialized Views for complex data modifications
* Implement logic in app layer when needed
* Use INSERT with deduplication for updates
* Consider using specialized table engines

### Error handling

* Implement proper error handling for unsupported features
* Have fallback approaches ready
* Log unsupported feature attempts
* Document workarounds for common issues

## See also

* [ClickHouse® Table Engines](/sql-reference/engines)
* [Working with Data Sources](/forward/core-concepts/data-sources)
* [Common function errors](/sql-reference/clickhouse-errors/UNSUPPORTED_METHOD)