A LineString
consists of
Point
values. You can extract particular
points of a LineString
, count the number of
points that it contains, or obtain its length.
Some functions in this section also work for
MultiLineString
values.
ST_EndPoint()
andEndPoint()
are synonyms. For more information, see the description ofST_EndPoint()
.Returns a double-precision number indicating the length of the
LineString
orMultiLineString
valuels
in its associated spatial reference. The length of aMultiLineString
value is equal to the sum of the lengths of its elements. If the argument isNULL
or an empty geometry, the return value isNULL
.mysql> SET @ls = 'LineString(1 1,2 2,3 3)'; mysql> SELECT GLength(GeomFromText(@ls)); +----------------------------+ | GLength(GeomFromText(@ls)) | +----------------------------+ | 2.8284271247461903 | +----------------------------+ mysql> SET @mls = 'MultiLineString((1 1,2 2,3 3),(4 4,5 5))'; mysql> SELECT GLength(GeomFromText(@mls)); +-----------------------------+ | GLength(GeomFromText(@mls)) | +-----------------------------+ | 4.242640687119286 | +-----------------------------+
GLength()
is a nonstandard name. It corresponds to the OpenGISLength()
function. (There is an existing SQL functionLength()
that calculates the length of string values.)ST_IsClosed()
andIsClosed()
are synonyms. For more information, see the description ofST_IsClosed()
.ST_NumPoints()
andNumPoints()
are synonyms. For more information, see the description ofST_NumPoints()
.ST_PointN()
andPointN()
are synonyms. For more information, see the description ofST_PointN()
.Returns the
Point
that is the endpoint of theLineString
valuels
. If the argument isNULL
or an empty geometry, the return value isNULL
.mysql> SET @ls = 'LineString(1 1,2 2,3 3)'; mysql> SELECT ST_AsText(ST_EndPoint(ST_GeomFromText(@ls))); +----------------------------------------------+ | ST_AsText(ST_EndPoint(ST_GeomFromText(@ls))) | +----------------------------------------------+ | POINT(3 3) | +----------------------------------------------+
ST_EndPoint()
andEndPoint()
are synonyms.For a
LineString
valuels
,ST_IsClosed()
returns 1 ifls
is closed (that is, itsST_StartPoint()
andST_EndPoint()
values are the same). If the argument isNULL
or an empty geometry, the return value isNULL
.For a
MultiLineString
valuels
,ST_IsClosed()
returns 1 ifls
is closed (that is, theST_StartPoint()
andST_EndPoint()
values are the same for eachLineString
inls
).ST_IsClosed()
returns 0 ifls
is not closed.mysql> SET @ls1 = 'LineString(1 1,2 2,3 3,2 2)'; mysql> SET @ls2 = 'LineString(1 1,2 2,3 3,1 1)'; mysql> SELECT ST_IsClosed(ST_GeomFromText(@ls1)); +------------------------------------+ | ST_IsClosed(ST_GeomFromText(@ls1)) | +------------------------------------+ | 0 | +------------------------------------+ mysql> SELECT ST_IsClosed(ST_GeomFromText(@ls2)); +------------------------------------+ | ST_IsClosed(ST_GeomFromText(@ls2)) | +------------------------------------+ | 1 | +------------------------------------+ mysql> SET @ls3 = 'MultiLineString((1 1,2 2,3 3),(4 4,5 5))'; mysql> SELECT ST_IsClosed(ST_GeomFromText(@ls3)); +------------------------------------+ | ST_IsClosed(ST_GeomFromText(@ls3)) | +------------------------------------+ | 0 | +------------------------------------+
ST_IsClosed()
andIsClosed()
are synonyms.Returns the number of
Point
objects in theLineString
valuels
. If the argument isNULL
or an empty geometry, the return value isNULL
.mysql> SET @ls = 'LineString(1 1,2 2,3 3)'; mysql> SELECT ST_NumPoints(ST_GeomFromText(@ls)); +------------------------------------+ | ST_NumPoints(ST_GeomFromText(@ls)) | +------------------------------------+ | 3 | +------------------------------------+
ST_NumPoints()
andNumPoints()
are synonyms.Returns the
N
-thPoint
in theLinestring
valuels
. Points are numbered beginning with 1. If any argument isNULL
or the geometry argument is an empty geometry, the return value isNULL
.mysql> SET @ls = 'LineString(1 1,2 2,3 3)'; mysql> SELECT ST_AsText(ST_PointN(ST_GeomFromText(@ls),2)); +----------------------------------------------+ | ST_AsText(ST_PointN(ST_GeomFromText(@ls),2)) | +----------------------------------------------+ | POINT(2 2) | +----------------------------------------------+
ST_PointN()
andPointN()
are synonyms.Returns the
Point
that is the start point of theLineString
valuels
. If the argument isNULL
or an empty geometry, the return value isNULL
.mysql> SET @ls = 'LineString(1 1,2 2,3 3)'; mysql> SELECT ST_AsText(ST_StartPoint(ST_GeomFromText(@ls))); +------------------------------------------------+ | ST_AsText(ST_StartPoint(ST_GeomFromText(@ls))) | +------------------------------------------------+ | POINT(1 1) | +------------------------------------------------+
ST_StartPoint()
andStartPoint()
are synonyms.ST_StartPoint()
andStartPoint()
are synonyms. For more information, see the description ofST_StartPoint()
.