# Geometry construction

Construct geometry values with CAST or write JSON coordinate arrays to a geometry column. The aliases define how coordinates nest and validate the resulting shape.

## Shapes

A Point is a pair of Float64 coordinates. MultiPoint, Ring and LineString are arrays of Points. A Polygon is an array of Rings, a MultiLineString is an array of LineStrings, and a MultiPolygon is an array of Polygons.

The declarations validate field types and nesting, not topological correctness. They do not detect self-intersections or assign a coordinate reference system.

## Examples

### A point and independent points

```sql
SELECT CAST('[1,2]' AS Point),
       CAST('[[1,2],[3,4]]' AS MultiPoint)
FORMAT csv;
```

```text
"[1,2]","[[1,2],[3,4]]"
```

### A polygon boundary

```sql
SELECT CAST('[[[0,0],[2,0],[2,2],[0,2]]]' AS Polygon)
FORMAT csv;
```

```text
"[[[0,0],[2,0],[2,2],[0,2]]]"
```

Use [point_in_polygon](https://coordinatordb.com/docs/reference/functions/regular-functions/geo/polygon) to test containment. See [geometry types](https://coordinatordb.com/docs/reference/data-types/geometry-types) for the alias table and [GeoJSON](https://coordinatordb.com/docs/reference/formats/geo-json) for interchange.