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LineString 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.
EndPoint(ls)
Point that is the end point of the LineString value
ls.
mysql> SELECT AsText(EndPoint(GeomFromText('LineString(1 1,2 2,3 3)')));
+------------------------------------------------------------+
| AsText(EndPoint(GeomFromText('LineString(1 1,2 2,3 3)'))) |
+------------------------------------------------------------+
| POINT(3 3) |
+------------------------------------------------------------+
|
GLength(ls)
LineString
value ls in its associated spatial reference.
mysql> SELECT GLength(GeomFromText('LineString(1 1,2 2,3 3)'));
+--------------------------------------------------+
| GLength(GeomFromText('LineString(1 1,2 2,3 3)')) |
+--------------------------------------------------+
| 2.8284271247462 |
+--------------------------------------------------+
|
IsClosed(ls)
LineString value ls is closed
(that is, its StartPoint() and EndPoint() values are the same).
Returns 0 if ls is not closed, and -1 if it is NULL.
mysql> SELECT IsClosed(GeomFromText('LineString(1 1,2 2,3 3)'));
+---------------------------------------------------+
| IsClosed(GeomFromText('LineString(1 1,2 2,3 3)')) |
+---------------------------------------------------+
| 0 |
+---------------------------------------------------+
|
NumPoints(ls)
LineString value ls.
mysql> SELECT NumPoints(GeomFromText('LineString(1 1,2 2,3 3)'));
+----------------------------------------------------+
| NumPoints(GeomFromText('LineString(1 1,2 2,3 3)')) |
+----------------------------------------------------+
| 3 |
+----------------------------------------------------+
|
PointN(ls,n)
n-th point in the Linestring value ls.
Point numbers begin at 1.
mysql> SELECT AsText(PointN(GeomFromText('LineString(1 1,2 2,3 3)'),2));
+-----------------------------------------------------------+
| AsText(PointN(GeomFromText('LineString(1 1,2 2,3 3)'),2)) |
+-----------------------------------------------------------+
| POINT(2 2) |
+-----------------------------------------------------------+
|
StartPoint(ls)
Point that is the start point of the LineString value
ls.
mysql> SELECT AsText(StartPoint(GeomFromText('LineString(1 1,2 2,3 3)')));
+-------------------------------------------------------------+
| AsText(StartPoint(GeomFromText('LineString(1 1,2 2,3 3)'))) |
+-------------------------------------------------------------+
| POINT(1 1) |
+-------------------------------------------------------------+
|
The OpenGIS specification also defines the following function, which MySQL does not implement:
IsRing(ls)
LineString value ls is closed
(that is, its StartPoint() and EndPoint() values are the same)
and is simple (does not pass through the same point more than once).
Returns 0 if ls is not a ring, and -1 if it is NULL.
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