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Add to_local_time() in function reference docs #11401

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merged 2 commits into from
Jul 11, 2024
Merged

Add to_local_time() in function reference docs #11401

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03ef4aa
chore: add document for `to_local_time()`
appletreeisyellow Jul 10, 2024
61c005f
chore: feedback
appletreeisyellow Jul 10, 2024
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65 changes: 64 additions & 1 deletion docs/source/user-guide/sql/scalar_functions.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1480,6 +1480,7 @@ contains(string, search_string)
- [make_date](#make_date)
- [to_char](#to_char)
- [to_date](#to_date)
- [to_local_time](#to_local_time)
- [to_timestamp](#to_timestamp)
- [to_timestamp_millis](#to_timestamp_millis)
- [to_timestamp_micros](#to_timestamp_micros)
Expand Down Expand Up @@ -1710,7 +1711,7 @@ to_char(expression, format)
#### Example

```
> > select to_char('2023-03-01'::date, '%d-%m-%Y');
> select to_char('2023-03-01'::date, '%d-%m-%Y');
+----------------------------------------------+
| to_char(Utf8("2023-03-01"),Utf8("%d-%m-%Y")) |
+----------------------------------------------+
Expand Down Expand Up @@ -1771,6 +1772,68 @@ to_date(expression[, ..., format_n])

Additional examples can be found [here](https://github.com/apache/datafusion/blob/main/datafusion-examples/examples/to_date.rs)

### `to_local_time`

Converts a timestamp with a timezone to a timestamp without a timezone (with no offset or
timezone information). This function handles daylight saving time changes.

```
to_local_time(expression)
```

#### Arguments

- **expression**: Time expression to operate on. Can be a constant, column, or function.

#### Example

```
> SELECT to_local_time('2024-04-01T00:00:20Z'::timestamp);
+---------------------------------------------+
| to_local_time(Utf8("2024-04-01T00:00:20Z")) |
+---------------------------------------------+
| 2024-04-01T00:00:20 |
+---------------------------------------------+

> SELECT to_local_time('2024-04-01T00:00:20Z'::timestamp AT TIME ZONE 'Europe/Brussels');
+---------------------------------------------+
| to_local_time(Utf8("2024-04-01T00:00:20Z")) |
+---------------------------------------------+
| 2024-04-01T00:00:20 |
+---------------------------------------------+

> SELECT
time,
arrow_typeof(time) as type,
to_local_time(time) as to_local_time,
arrow_typeof(to_local_time(time)) as to_local_time_type
FROM (
SELECT '2024-04-01T00:00:20Z'::timestamp AT TIME ZONE 'Europe/Brussels' AS time
);
+---------------------------+------------------------------------------------+---------------------+-----------------------------+
| time | type | to_local_time | to_local_time_type |
+---------------------------+------------------------------------------------+---------------------+-----------------------------+
| 2024-04-01T00:00:20+02:00 | Timestamp(Nanosecond, Some("Europe/Brussels")) | 2024-04-01T00:00:20 | Timestamp(Nanosecond, None) |
+---------------------------+------------------------------------------------+---------------------+-----------------------------+

# combine `to_local_time()` with `date_bin()` to bin on boundaries in the timezone rather
# than UTC boundaries

> SELECT date_bin(interval '1 day', to_local_time('2024-04-01T00:00:20Z'::timestamp AT TIME ZONE 'Europe/Brussels')) AS date_bin;
+---------------------+
| date_bin |
+---------------------+
| 2024-04-01T00:00:00 |
+---------------------+

> SELECT date_bin(interval '1 day', to_local_time('2024-04-01T00:00:20Z'::timestamp AT TIME ZONE 'Europe/Brussels')) AT TIME ZONE 'Europe/Brussels' AS date_bin_with_timezone;
+---------------------------+
| date_bin_with_timezone |
+---------------------------+
| 2024-04-01T00:00:00+02:00 |
+---------------------------+
```

### `to_timestamp`

Converts a value to a timestamp (`YYYY-MM-DDT00:00:00Z`).
Expand Down