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# ST_ConcaveHull

Return the Concave Hull of polygon A, with alpha set to pctConvex\[0, 1] in the Delaunay Triangulation method, the concave hull will not contain a hole unless allowHoles is set to true

<img src="https://mintcdn.com/wherobots/fqh3gPDE0J25Lra_/images/sql-functions/ST_ConcaveHull/ST_ConcaveHull.svg?fit=max&auto=format&n=fqh3gPDE0J25Lra_&q=85&s=4c6bf2aa8d3bd0d45529600d053e7311" alt="ST_ConcaveHull" width="500" height="300" data-path="images/sql-functions/ST_ConcaveHull/ST_ConcaveHull.svg" />

## Signatures

```sql theme={"system"}
ST_ConcaveHull (A: Geometry, pctConvex: Double)
```

```sql theme={"system"}
ST_ConcaveHull (A: Geometry, pctConvex: Double, allowHoles: Boolean)
```

## Parameters

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

<ParamField body="pctConvex" type="Double" required>
  The pct convex value.
</ParamField>

<ParamField body="allowHoles" type="Boolean">
  The allow holes value.
</ParamField>

## Return type

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

## Example

```sql theme={"system"}
SELECT ST_ConcaveHull(ST_GeomFromWKT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'), 1)
```

```
POLYGON ((125 100, 20 40, 50 60, 175 150, 125 100))
```