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# ST_Boundary

Returns the closure of the combinatorial boundary of this Geometry.

<img src="https://mintcdn.com/wherobots/AayJA2u8CknIeTgt/images/sql-functions/ST_Boundary/ST_Boundary.svg?fit=max&auto=format&n=AayJA2u8CknIeTgt&q=85&s=07e0867398ccfe4d82d9c4efec8b4a23" alt="ST_Boundary" width="500" height="300" data-path="images/sql-functions/ST_Boundary/ST_Boundary.svg" />

## Signatures

```sql theme={"system"}
ST_Boundary(geom: Geometry)
```

## Parameters

<ParamField body="geom" type="Geometry" required>
  The input geometry.
</ParamField>

## Return type

<ResponseField type="Geometry">
  The resulting geometry.
</ResponseField>

## Example

```sql theme={"system"}
SELECT ST_Boundary(ST_GeomFromWKT('POLYGON((1 1,0 0, -1 1, 1 1))'))
```

```
LINESTRING (1 1, 0 0, -1 1, 1 1)
```