STV_LineStringPoint
检索线串或线串集合的顶点。 根据输入对象的类型，返回的值为 GEOMETRY 或 GEOGRAPHY 类型的点。GEOMETRY 点将继承输入对象的 SRID。
STV_LineStringPoint 为分析函数。有关详细信息，请参阅分析函数。
行为类型
不可变语法
STV_LineStringPoint( g )
OVER( [PARTITION NODES] ) AS
参数
g- 线串或线串集合，GEOMETRY 或 GEOGRAPHY 类型的值
返回
GEOMETRY 或 GEOGRAPHY
支持的数据类型
示例
以下示例显示了 STV_LineStringPoint 的用法。
返回几何线串的顶点及其 SRID：
=> SELECT ST_AsText(Point), ST_SRID(Point)
FROM (SELECT STV_LineStringPoint(
ST_GeomFromText('MULTILINESTRING((1 2, 2 3, 3 1, 4 2),
(10 20, 20 30, 30 10, 40 20))', 4269)) OVER () AS Point) AS foo;
ST_AsText | ST_SRID
---------------+---------
POINT (1 2) | 4269
POINT (2 3) | 4269
POINT (3 1) | 4269
POINT (4 2) | 4269
POINT (10 20) | 4269
POINT (20 30) | 4269
POINT (30 10) | 4269
POINT (40 20) | 4269
(8 rows)
返回地理线串的顶点：
=> SELECT ST_AsText(g)
FROM (SELECT STV_LineStringPoint(
ST_GeographyFromText('MULTILINESTRING ((42.1 71.0, 41.4 70.0, 41.3 72.9),
(42.99 71.46, 44.47 73.21)', 4269)) OVER () AS g) AS line_geog_points;
ST_AsText
---------------------
POINT (42.1 71.0)
POINT (41.4 70.0)
POINT (41.3 72.9)
POINT (42.99 71.46)
POINT (44.47 73.21)
(5 rows)