• ST_Geometry type

• ST_CircularString type
• ST_CompoundCurve type
• ST_LineString type

• ST_CurveToLine method for type ST_Curve
• ST_EndPoint method for type ST_Curve
• ST_IsClosed method for type ST_Curve
• ST_IsRing method for type ST_Curve
• ST_Length method for type ST_Curve
• ST_StartPoint method for type ST_Curve
• All methods of ST_Geometry type can also be called on a ST_Curve type.

The ST_Curve type is a supertype for types representing lines using a sequence of points. Subtypes specify whether the control points are joined using straight segments (ST_LineString), circular segments (ST_CircularString) or a combination (ST_CompoundCurve). The ST_Curve type is not instantiable. An ST_Curve value is simple if it does not intersect itself (except possibly at the end points). If an ST_Curve value does intersect at its endpoints, it is closed. An ST_Curve value that is both simple and closed is called a ring.