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

# ST_Union (Python)

> Calculate the union of two geometries.

Calculate the union of two geometries.

SQL reference: [`ST_Union`](/reference/wherobots-db/geometry-data/overlay/ST_Union)

## Signature

```python theme={"system"}
from sedona.spark.sql.st_functions import ST_Union

ST_Union(a: ColumnOrName, b: Optional[ColumnOrName] = None) -> Column
```

## Parameters

<ParamField path="a" type="ColumnOrName" required>
  One geometry column to use.
</ParamField>

<ParamField path="b" type="Optional[ColumnOrName]" default="None">
  Other geometry column to use.
</ParamField>

## Returns

<ResponseField name="return" type="Column">
  Geometry representing the union of a and b as a geometry column.
</ResponseField>


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