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# KATER__HOUR

The start of the hour the timestamp is in.

{/* Written by apps/landing-page/scripts/docs/write_kater_functions.py from the compiler's function registry, kater_sql/function_docs.py and scripts/docs/sql-language.md. Do not edit it by hand: change those, then run the script. */}

**Family:** [Date grains](https://kater.ai/docs/sql-reference/functions/date-grains/)

## Syntax

```sql
KATER__HOUR(field)
```

## Arguments

| Argument | Description |
| --- | --- |
| `field` | The timestamp, or a time of day. |

## Returns

A timestamp.

## Usage notes

- A date has no time of day, so the compiler refuses it on a date.

## Example

This Sandbox query reads the sample shop's orders. The table shows the rows that Kater gave.

```sql {4}
SELECT
  orders.order_id AS "Order ID",
  orders.ordered_at AS "Ordered At",
  DIMENSION('ordered_at_hour', KATER__HOUR(orders.ordered_at)) AS "Hour"
FROM kater_dataset.orders AS orders
ORDER BY
  1
LIMIT 3
```

| Order ID | Ordered At | Hour |
| --- | --- | --- |
| O00000 | 2025-05-26T09:02:00 | 2025-05-26T09:00:00 |
| O00001 | 2025-11-28T09:21:00 | 2025-11-28T09:00:00 |
| O00002 | 2025-07-25T13:56:00 | 2025-07-25T13:00:00 |

## Compiles to

The call compiles to the same SQL on DuckDB and on Snowflake.

```sql
DATE_TRUNC('HOUR', orders.ordered_at)
```

## See also

- [Dates](https://kater.ai/docs/model/fields/dimensions/dates/)
- Other functions in [Date grains](https://kater.ai/docs/sql-reference/functions/date-grains/): [`KATER__DATE`](https://kater.ai/docs/sql-reference/functions/kater__date/), [`KATER__WEEK`](https://kater.ai/docs/sql-reference/functions/kater__week/), [`KATER__MONTH`](https://kater.ai/docs/sql-reference/functions/kater__month/), [`KATER__QUARTER`](https://kater.ai/docs/sql-reference/functions/kater__quarter/), [`KATER__YEAR`](https://kater.ai/docs/sql-reference/functions/kater__year/), [`KATER__MINUTE`](https://kater.ai/docs/sql-reference/functions/kater__minute/), [`KATER__SECOND`](https://kater.ai/docs/sql-reference/functions/kater__second/), [`KATER__MILLISECOND`](https://kater.ai/docs/sql-reference/functions/kater__millisecond/)

On this page

Syntax
Arguments
Returns
Usage notes
Example
Compiles to
See also

Kater SQL Functions Date grains

KATER__HOUR

The start of the hour the timestamp is in.

Family: Date grains

Syntax

1
KATER__HOUR(field)

Arguments

Argument	Description
`field`	The timestamp, or a time of day.

Returns

A timestamp.

Usage notes

A date has no time of day, so the compiler refuses it on a date.

Example

This Sandbox query reads the sample shop’s orders. The table shows the rows that Kater gave.

1
SELECT
2
  orders.order_id AS "Order ID",
3
  orders.ordered_at AS "Ordered At",
4
  DIMENSION('ordered_at_hour', KATER__HOUR(orders.ordered_at)) AS "Hour"
5
FROM kater_dataset.orders AS orders
6
ORDER BY
7
  1
8
LIMIT 3

Order ID	Ordered At	Hour
O00000	2025-05-26T09:02:00	2025-05-26T09:00:00
O00001	2025-11-28T09:21:00	2025-11-28T09:00:00
O00002	2025-07-25T13:56:00	2025-07-25T13:00:00

Compiles to

The call compiles to the same SQL on DuckDB and on Snowflake.

1
DATE_TRUNC('HOUR', orders.ordered_at)

See also

Dates
Other functions in Date grains: KATER__DATE, KATER__WEEK, KATER__MONTH, KATER__QUARTER, KATER__YEAR, KATER__MINUTE, KATER__SECOND, KATER__MILLISECOND