ST_Perimeter method

surface-expression.ST_Perimeter([ unit-name])

Name	Type	Description
unit-name	VARCHAR(128)	The units in which the length should be computed. Defaults to the unit of the spatial reference system. The unit name must match the UNIT_NAME column of a row in the ST_UNITS_OF_MEASURE view where UNIT_TYPE is 'LINEAR'.

DOUBLE Returns the perimeter of the surface in the specified unit of measure.

The ST_Perimeter method returns the length of the perimeter of a surface in the units identified by the unit-name parameter. If the surface is empty, then NULL is returned.

If the surface contains Z values, these are not considered when computing the perimeter of the geometry.

The perimeter of a polygon includes the length of all rings (exterior and interior).

Note

If the surface-expression is an empty geometry (ST_IsEmpty()=1), then this method returns NULL.

Note

By default, ST_Perimeter 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.

SQL/MM (ISO/IEC 13249-3: 2006) 8.1.3

The following example returns the result 18.

SELECT TREAT( Shape as ST_Surface ).ST_Perimeter()
FROM SpatialShapes WHERE ShapeID = 3

The following returns the perimeter of the poly_geometry column in miles from the fictional region table.

SELECT name, poly_geometry.ST_Perimeter( 'Statute Mile' )
FROM region