---
title: ES|QL ST_UNION function
description:
url: https://www.elastic.co/elastic/docs-builder/docs/3562/reference/query-languages/esql/functions-operators/spatial-functions/st_union
products:
- Elasticsearch
---
# ES|QL ST_UNION function
- Elastic Cloud Serverless: Preview
- Elastic Stack: Planned
Returns the geometric union of two geometries.
## Syntax
## Parameters
Expression of type `geo_point`, `geo_shape`, `cartesian_point` or `cartesian_shape`. If `null`, the function returns `null`.
Expression of type `geo_point`, `geo_shape`, `cartesian_point` or `cartesian_shape`. Must share the same coordinate reference system as the first parameter. If `null`, the function returns `null`.
## Description
Returns the geometric union of two geometries. The result is a geometry that covers all points covered by either input geometry. Both geometries must share the same coordinate reference system.
## Supported types
| geomA | geomB | result |
|-----------------|-----------------|-----------------|
| cartesian_point | cartesian_point | cartesian_shape |
| cartesian_point | cartesian_shape | cartesian_shape |
| cartesian_shape | cartesian_point | cartesian_shape |
| cartesian_shape | cartesian_shape | cartesian_shape |
| geo_point | geo_point | geo_shape |
| geo_point | geo_shape | geo_shape |
| geo_shape | geo_point | geo_shape |
| geo_shape | geo_shape | geo_shape |
## Example
```esql
ROW a = TO_GEOSHAPE("POLYGON ((0 0, 2 0, 2 2, 0 2, 0 0))"),
b = TO_GEOSHAPE("POLYGON ((2 0, 4 0, 4 2, 2 2, 2 0))")
| EVAL unioned = ST_UNION(a, b)
| KEEP unioned
```
| unioned:geo_shape |
|---------------------------------------------------------------------------|
| POLYGON ((2.0 0.0, 0.0 0.0, 0.0 2.0, 2.0 2.0, 4.0 2.0, 4.0 0.0, 2.0 0.0)) |
### Diagrams
**Union of two overlapping polygons**
The union of two overlapping squares covers the area of both.
