curve-expression.ST_IsRing()

• ST_IsClosed method for type ST_Curve
• ST_IsSimple method for type ST_Geometry

The following returns all rows in SpatialShapes containing rings. The IF expression is required to ensure the TREAT function is not executed if the Shape is not a subtype of ST_Curve. Without the IF expression the server may reorder the conditions in the WHERE clause, leading to an error.

SELECT * FROM SpatialShapes 
WHERE IF Shape IS OF ( ST_Curve )
         AND TREAT( Shape AS ST_Curve ).ST_IsRing() = 1 THEN 1 ENDIF = 1

The following returns all rows in curve_table that have geometries that are rings. This example assumes the geometry column has type ST_Curve, ST_LineString, ST_CircularString or ST_CompoundCurve.

SELECT * FROM curve_table WHERE geometry.ST_IsRing() = 1