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

# AS CHANGELOG

> Use the `AS CHANGELOG` clause to convert a changelog operation in a stream into a column.

This can be used to create materialized views and sinks. See the practice in [Sink data with upsert in Snowflake](/integrations/destinations/snowflake#sink-data-with-upsert).

The AS CHANGELOG clause adds two metadata columns:

* `changelog_op`: the change type (`1` = Insert, `2` = Delete, `3` = UpdateInsert, `4` = UpdateDelete)
* `_changelog_row_id`: a monotonically increasing identifier that captures the order of the change.

## Syntax

```sql theme={null}
WITH table_name AS CHANGELOG FROM source_table;
```

This is done using the CTE syntax. It converts the `source_table` change record to a column of `table_name`.

## Example

```sql Create MV theme={null}
CREATE MATERIALIZED VIEW ss_mv AS
WITH sub AS CHANGELOG FROM user_behaviors
SELECT
    user_id,
    target_id,
    event_timestamp AT TIME ZONE 'America/Indiana/Indianapolis' AS event_timestamp,
    changelog_op AS __op,
    _changelog_row_id::bigint AS __row_id
FROM
    sub;
```

```sql Changelog operation theme={null}
INSERT INTO user_behaviors (v1, v2) VALUES (1, 1);
INSERT INTO user_behaviors (v1, v2) VALUES (2, 2);

DELETE FROM user_behaviors WHERE v1 = 2;

UPDATE user_behaviors SET v2 = 100 WHERE v1 = 1;

```

```sql Query MV theme={null}
SELECT * FROM ss_mv;

-------RESULT
v1  v2  changelog_op
1   1   1
2   2   1
2   2   2
1   1   4
1   100 3
```