Amazon Redshift will no longer support the creation of new Python UDFs starting Patch 198. Existing Python UDFs will continue to function until June 30, 2026. For more information, see the [ blog post ](https://aws.amazon.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/). 

# ST\$1Union
<a name="ST_Union-function"></a>

ST\$1Union returns a geometry representing the union of two geometries. That is, it merges the input geometries to produce a resulting geometry with no overlaps. 

## Syntax
<a name="ST_Union-function-syntax"></a>

```
ST_Union(geom1, geom2)
```

## Arguments
<a name="ST_Union-function-arguments"></a>

 *geom1*   
A value of data type `GEOMETRY` or an expression that evaluates to a `GEOMETRY` type. 

 *geom2*   
A value of data type `GEOMETRY` or an expression that evaluates to a `GEOMETRY` type. 

## Return type
<a name="ST_Union-function-return"></a>

`GEOMETRY`

The spatial reference system identifier (SRID) value of the returned geometry is the SRID value of the input geometries.

If *geom1* or *geom2* is null, then null is returned. 

If *geom1* or *geom2* are empty, then an empty geometry is returned. 

If *geom1* and *geom2* don't have the same value for the spatial reference system identifier (SRID), then an error is returned. 

If *geom1* or *geom2* is a geometry collection, linestring, or multilinestring, then an error is returned. 

If *geom1* or *geom2* is not a two-dimensional (2D) geometry, then an error is returned. 

## Examples
<a name="ST_Union-function-examples"></a>

The following SQL returns the non-empty geometry representing the union of two input geometries. 

```
SELECT ST_AsEWKT(ST_Union(ST_GeomFromText('POLYGON((0 0,100 100,0 200,0 0))'), ST_GeomFromText('POLYGON((0 0,10 0,0 10,0 0))')));
```

```
        st_asewkt        
-------------------------
 POLYGON((0 0,0 200,100 100,5 5,10 0,0 0))
```