> For the complete documentation index, see [llms.txt](https://upsolver.gitbook.io/content/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://upsolver.gitbook.io/content/reference-1/sql-commands/iceberg-tables/upsolver-managed-tables/alter-iceberg-table.md).

# ALTER ICEBERG TABLE

## Syntax

### **Changing table options**

Alters  previously configured options for the specified Apache Iceberg table:

```sql
ALTER ICEBERG TABLE <table_identifier> 
    SET <table_option> = <value>;
```

### **Partitioning/Clustering**

Users can change the partition or cluster columns of an existing table. Additionally, you can switch from partitioning to clustering and vice versa, with these changes applying to data moving forward.

**Changing columns**

Changes the partition/cluster columns of an existing table. This change does not rebuild the existing data according to the new partitioning, but will apply the new partitioning to data moving forward.

Partitioned table example:

```sql
ALTER TABLE <table_name> PARTITION BY <column_name> [, ...];
```

Clustered table example:

```sql
ALTER TABLE <table_name> CLUSTER BY <column_name> [, ...];
```

Note  you can use any [partition transforms](https://iceberg.apache.org/spec/#partition-transforms) supported by iceberg. for example:

```sql
ALTER TABLE <table_name> PARTITION BY
  TRUNCATE(10, <column_name>),
  DAY(<timestamp_column_name>);
```

**Stop partitioning\clustering**&#x20;

To stop table partitioning or clustering moving forward:

```sql
ALTER TABLE <table_name> PARTITION BY ();
```

#### Switching Between Partitioning and Clustering

You can also change the table structure from clustering to partitioning and vice versa, which will apply to data moving forward.

### **Sorting evolution**&#x20;

Changes the sorting columns of an existing table.

This will affect the data written from now onwards and new compactions will write data using the new sorting.

```sql
ALTER TABLE <table_name> ORDER BY <column_name> [ASC | DESC] [, ...]
```

To disable sorting completely:

```sql
ALTER TABLE <table_name> ORDER BY ()
```

If you wishes to re-sort old data after changing the sorting, you can trigger a compaction with [OPTIMIZE TABLE](/content/reference-1/sql-commands/iceberg-tables/upsolver-managed-tables/optimize-iceberg-table.md) command.

### Examples

Modifying table options:

<pre class="language-sql"><code class="lang-sql">ALTER ICEBERG TABLE my_iceberg_table
SET compute_cluster = "my_compute_cluster",
<strong>iceberg.read.split."planning-lookback"='10';
</strong></code></pre>

Changing partitions columns:

```sql
ALTER ICEBERG TABLE my_iceberg_table PARTITION BY COLUMN1, COLUMNS2;
```

Changing Sort columns:

```sql
ALTER ICEBERG TABLE my_iceberg_table ORDER BY COLUMN1 DESC, COLUMNS2 ASC;
```

{% hint style="warning" %}
`Note` that not all table options are mutable.&#x20;

All mutable options are denoted by **— editable** in the individual option descriptions.
{% endhint %}

To check if a certain table option is mutable, see [CREATE ICEBERG TABLE](/content/reference-1/sql-commands/iceberg-tables/upsolver-managed-tables/create-iceberg-table.md).


---

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