# ST_Length function

The ST_Length function takes a curve or multicurve and, optionally, a unit as input parameters and returns the length of the given curve or multicurve in the default or given unit of measure.

If the given curve or multicurve is null or is empty, null is returned.

This function can also be called as a method.

## Syntax

## Parameter

- curve
- A value of type ST_Curve or ST_MultiCurve that represents the curves for which the length is returned.
- unit
- A VARCHAR(128) value that identifies the units in which the length of the curve is measured. The supported units of measure are listed in the DB2GSE.ST_UNITS_OF_MEASURE catalog view.

If the

*unit*parameter is omitted, the following rules are used to determine the unit in which the length is measured:- If
*curve*is in a projected or geocentric coordinate system, the linear unit associated with this coordinate system is the default. - If
*curve*is in a geographic coordinate system, the angular unit associated with this coordinate system is the default.

**Restrictions on unit conversions:**An error (SQLSTATE 38SU4) is returned if any of the following conditions occur:

- The
*curve*is in an unspecified coordinate system and the*unit*parameter is specified. - The
*curve*is in a projected coordinate system and an angular unit is specified. - The
*curve*is in a geographic coordinate system, and a linear unit is specified.

## Return type

DOUBLE