multicurve-expression.ST_Length([ unit-name])

The ST_Length method returns the length of a multicurve in the units identified by the unit-name parameter. The length of a multicurve is the sum of the lengths of the contained curves. If the curve is empty, then NULL is returned.

If the curve contains Z values, these are not considered when computing the length of the geometry.

• ST_Length method for type ST_Curve

The following example creates a multicurve and uses ST_Length to find the length of the geometry, returning the value PI+1.

SELECT NEW ST_MultiCurve( 
	    NEW ST_LineString('LineString (0 0, 1 0)' ), 
	    NEW ST_CircularString( 'CircularString( 0 0, 1 1, 2 0)' ) )
	.ST_Length()

The following example returns the name and length of all roads longer than 100 miles. This example assumes the road table exists, that the geometry column has type ST_MultiCurve or ST_MultiLineString, and the sa_install_feature system procedure has been used to load the st_geometry_predefined_uom.

SELECT name, geometry.ST_Length( 'Statute Mile' ) len
FROM roads WHERE len > 100