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

> Reference for Iceberg functions

# Iceberg functions

For an overview of querying, tuning, and exporting Iceberg tables, see the [Iceberg guide](/guides/iceberg-and-data-lake/iceberg).

## Iceberg functions

Iceberg functions provide utilities for working with [Apache Iceberg](https://iceberg.apache.org/) tables. These functions include table-valued functions for reading Iceberg data and partition transform functions that implement the [Iceberg partition transforms specification](https://iceberg.apache.org/spec/#partition-transforms).

### Reading Iceberg data

Read Iceberg tables ad hoc with the [`READ_ICEBERG`](/reference-sql/functions-reference/iceberg/read_iceberg) table-valued function, register them in Firebolt's catalog with [`CREATE ICEBERG TABLE`](/reference-sql/commands/data-definition/create-iceberg-table), or mount an entire catalog with [`CREATE ICEBERG DATABASE`](/reference-sql/commands/data-definition/create-iceberg-database). For how to choose between these approaches and tune them, see the [Iceberg guide](/guides/iceberg-and-data-lake/iceberg).

### Partition transform functions

Iceberg partition transform functions compute partition values according to the [Iceberg specification](https://iceberg.apache.org/spec/#partition-transforms). These functions can be used in the `PARTITION BY` clause of [`CREATE ICEBERG TABLE`](/reference-sql/commands/data-definition/create-iceberg-table-as-select) commands.

```sql theme={"theme":{"light":"css-variables","dark":"css-variables"}}
SELECT 
  iceberg_year('2025-12-15'::DATE) AS year_partition,
  iceberg_month('2025-12-15'::DATE) AS month_partition,
  iceberg_day('2025-12-15'::DATE) AS day_partition;
```

**Returns:**

| year\_partition | month\_partition | day\_partition |
| :-------------- | :--------------- | :------------- |
| 55              | 671              | 20437          |

### Available functions

**Table-valued functions:**

* [`READ_ICEBERG`](/reference-sql/functions-reference/iceberg/read_iceberg) - Read data from Iceberg tables

**Partition transform functions:**

* [`ICEBERG_YEAR`](/reference-sql/functions-reference/iceberg/partitioning/iceberg_year) - Extract year as years from 1970
* [`ICEBERG_MONTH`](/reference-sql/functions-reference/iceberg/partitioning/iceberg_month) - Extract month as months from 1970-01-01
* [`ICEBERG_DAY`](/reference-sql/functions-reference/iceberg/partitioning/iceberg_day) - Extract day as days from 1970-01-01
* [`ICEBERG_HOUR`](/reference-sql/functions-reference/iceberg/partitioning/iceberg_hour) - Extract hour as hours from 1970-01-01 00:00:00
* [`ICEBERG_BUCKET`](/reference-sql/functions-reference/iceberg/partitioning/iceberg_bucket) - Hash value into a bucket
* [`ICEBERG_TRUNCATE`](/reference-sql/functions-reference/iceberg/partitioning/iceberg_truncate) - Truncate value to a width