12.15.7.3 LineString and MultiLineString Property Functions

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.

• EndPoint(ls)

  ST_EndPoint() and EndPoint() are synonyms. For more information, see the description of ST_EndPoint().

• GLength(ls)

  Returns a double-precision number indicating the length of the LineString or MultiLineString value ls in its associated spatial reference. The length of a MultiLineString value is equal to the sum of the lengths of its elements.

  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 OpenGIS Length() function. (There is an existing SQL function Length() that calculates the length of string values.)

• IsClosed(ls)

  ST_IsClosed() and IsClosed() are synonyms. For more information, see the description of ST_IsClosed().

• NumPoints(ls)

  ST_NumPoints() and NumPoints() are synonyms. For more information, see the description of ST_NumPoints().

• PointN(ls, N)

  ST_PointN() and PointN() are synonyms. For more information, see the description of ST_PointN().

• ST_EndPoint(ls)

  Returns the Point that is the endpoint of the LineString value ls.

  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() and EndPoint() are synonyms.

  ST_EndPoint() was added in MySQL 5.6.1.

• ST_IsClosed(ls)

  For a LineString value ls, ST_IsClosed() returns 1 if ls is closed (that is, its ST_StartPoint() and ST_EndPoint() values are the same).

  For a MultiLineString value ls, ST_IsClosed() returns 1 if ls is closed (that is, the ST_StartPoint() and ST_EndPoint() values are the same for each LineString in ls).

  ST_IsClosed() returns 0 if ls is not closed, and NULL if ls is NULL.

  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() and IsClosed() are synonyms.

  ST_IsClosed() was added in MySQL 5.6.1.

• ST_NumPoints(ls)

  Returns the number of Point objects in the LineString value ls.

  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() and NumPoints() are synonyms.

  ST_NumPoints() was added in MySQL 5.6.1.

• ST_PointN(ls, N)

  Returns the N-th Point in the Linestring value ls. Points are numbered beginning with 1.

  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() and PointN() are synonyms.

  ST_PointN() was added in MySQL 5.6.1.

• ST_StartPoint(ls)

  Returns the Point that is the start point of the LineString value ls.

  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() and StartPoint() are synonyms.

  ST_StartPoint() was added in MySQL 5.6.1.

• StartPoint(ls)

  ST_StartPoint() and StartPoint() are synonyms. For more information, see the description of ST_StartPoint().