st_geomfromtext
时间: 2023-12-14 14:02:58 浏览: 40
ST_GeomFromText is a function in PostgreSQL's PostGIS extension that converts a well-known text (WKT) representation of a geometry into a PostGIS geometry object. The function takes a single argument, the WKT string, and returns the corresponding geometry object.
For example, to convert a WKT string representing a point into a PostGIS point geometry object:
```
SELECT ST_GeomFromText('POINT(45.5231,-122.6765)');
```
This will return a PostGIS point geometry object with the coordinates (45.5231, -122.6765).
ST_GeomFromText can also be used to convert other types of geometries, such as lines and polygons, as well as more complex geometries like multi-points and multi-polygons.
相关问题
在kingbase 创建一个ST_GeomFromText函数
Kingbase已经提供了ST_GeomFromText函数,您可以直接使用它。
如果您需要在Kingbase中创建自定义的ST_GeomFromText函数,可以按照以下步骤进行操作:
1. 使用CREATE FUNCTION语句创建一个新的函数:
```
CREATE FUNCTION my_geomfromtext(text) RETURNS geometry AS $$
DECLARE
g geometry;
BEGIN
-- 在这里编写自己的ST_GeomFromText函数逻辑
-- 可以使用Kingbase中的ST_GeomFromText函数作为基础
g := ST_GeomFromText($1);
RETURN g;
END;
$$ LANGUAGE plpgsql;
```
在这个例子中,我们创建了一个名为"my_geomfromtext"的函数,它接受一个文本参数,并返回一个geometry类型的对象。
2. 使用SELECT语句测试函数:
```
SELECT my_geomfromtext('POINT(1 1)');
```
在这个例子中,我们使用"my_geomfromtext"函数将一个文本表示的点转换为geometry对象,并将其输出到结果集中。
现在,您已经成功地在Kingbase中创建了一个自定义的ST_GeomFromText函数。请注意,您需要使用PL/pgSQL语言编写函数,并使用Kingbase中的ST_函数来执行空间操作。
st_geomfromtext('${pointWkt}', 4326)
This code snippet is used in SQL queries to create a geometry object from a Well-Known Text (WKT) representation of a point. The pointWkt variable contains the WKT representation of the point, and 4326 is the spatial reference identifier (SRID) for the WGS 84 coordinate system.
The function st_geomfromtext() is a spatial function in PostGIS, a spatial extension for PostgreSQL. It creates a geometry object from a text representation of a geometry in WKT or GeoJSON format.
Example usage:
SELECT ST_AsText(ST_GeomFromText('POINT(-122.34900 47.65100)', 4326));
The above query will create a point geometry object from the WKT representation 'POINT(-122.34900 47.65100)', which represents a point at the longitude -122.34900 and latitude 47.65100, in the WGS 84 coordinate system. The ST_AsText() function will convert the geometry object back to a WKT representation, which will be 'POINT(-122.349 47.651)'.
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