ST_IsClosed method

Test if the ST_Curve value is closed. A curve is closed if the start and end points are coincident.

Note

By default, ST_IsClosed uses the original format for a geometry, if it is available. Otherwise, the internal format is used. For more information about internal and original formats, see STORAGE FORMAT clause, CREATE SPATIAL REFERENCE SYSTEM statement.

Syntax

curve-expression.ST_IsClosed()

Returns

Standards and compatibility

Example

The following returns all rows in SpatialShapes containing closed curves. 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_IsClosed() = 1 THEN 1 ENDIF = 1

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

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

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