> ## 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.

# COMMENT ON

> You can use the `COMMENT ON` command to add comments on tables or columns in RisingWave. Comments are stored as metadata of tables or columns.

If you want to remove an existing comment on a table or column, rewrite the current comment with `NULL`.

## Syntax

```sql theme={null}
COMMENT ON <object_type> <relation_name>.<object_name> IS <comment>
```

## Parameters

| Parameter                     | Notes                                                                                                      |
| :---------------------------- | :--------------------------------------------------------------------------------------------------------- |
| *object\_type*                | Type of the object that you want to add comments to. Allowed values: TABLE, COLUMN.                        |
| *relation\_name.object\_name* | Name of the object that you want to add comments to. For columns, you also need to specify the table name. |
| *comment*                     | Comment that you want to add.                                                                              |

## Examples

Add a comment on a table:

```sql theme={null}
COMMENT ON TABLE t1 IS 'table to store traffic data';
```

Add a comment to a column:

```sql theme={null}
COMMENT ON COLUMN t1.v1 IS 'column for the duration of the trip';
```

Remove the comment on a table:

```sql theme={null}
COMMENT ON table t1 IS NULL;
```

After a comment is added to a table or column, you can display it in these ways:

1. Using the `rw_description` table:

```sql theme={null}
SELECT * FROM rw_description;
------
 objoid | classoid | objsubid |             description
--------+----------+----------+-------------------------------------
   1001 |       41 |          | table to store traffic data
   1001 |       41 |        1 | column for the duration of the trip
   1001 |       41 |        2 |
   1001 |       41 |        0 |
```

2. Using the `SHOW COLUMNS` or `DESCRIBE` command:

```sql theme={null}
SHOW COLUMNS FROM t1;
```

```sql theme={null}
DESCRIBE t1;
```

## Related topics

<CardGroup>
  <Card title="DESCRIBE" icon="circle-info" iconType="solid" href="/sql/commands/sql-describe" horizontal />
</CardGroup>