Spatial data types

A spatially enabled database supplies a hierarchy of geometry data types.

Figure 1 presents this hierarchy. In this figure, the instantiable types have a white background; the uninstantiable types have a shaded background.

Instantiable data types are ST_Point, ST_LineString, ST_Polygon, ST_Geometry, ST_GeomCollection, ST_MultiPoint, ST_MultiPolygon, and ST_MultiLineString.

Data types that are not instantiable are ST_Curve, ST_Surface, ST_MultiSurface, and ST_MultiCurve.
Figure 1. Hierarchy of spatial data types. Data types named in white boxes are instantiable. Data types named in shaded boxes are not instantiable.
top Instantiable and not instantiable data types
The hierarchy in Figure 1 includes:
  • Data types for geographic features that can be perceived as forming a single unit; for example, individual residences and isolated lakes.
  • Data types for geographic features that are made up of multiple units or components; for example, canal systems and groups of islands in a lake.
  • A data type for geographic features of all kinds.