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# ST_IsSimple

Test if geometry's only self-intersections are at boundary points.

<img src="https://mintcdn.com/wherobots/fqh3gPDE0J25Lra_/images/sql-functions/ST_IsSimple/ST_IsSimple.svg?fit=max&auto=format&n=fqh3gPDE0J25Lra_&q=85&s=3743c87562b3ae2fdd9ac8e9022a41e7" alt="ST_IsSimple" width="500" height="300" data-path="images/sql-functions/ST_IsSimple/ST_IsSimple.svg" />

## Signatures

```sql theme={"system"}
ST_IsSimple (A: Geometry)
```

## Parameters

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

## Return type

<ResponseField type="Boolean">
  Returns `true` or `false`.
</ResponseField>

## Example

```sql theme={"system"}
SELECT ST_IsSimple(ST_GeomFromWKT('POLYGON((1 1, 3 1, 3 3, 1 3, 1 1))'))
```

```
true
```