STV_Extent

返回一个包含所有输入数据的边界框。

在嵌套查询中使用 STV_Extent 以获得最佳结果。OVER 子句必须为空。

重要

当输入为单点时，STV_Extent 不会返回有效的多边形。

行为类型

语法

STV_Extent( g )

参数

g: 空间对象，类型为 GEOMETRY。

GEOMETRY

支持的数据类型

数据类型: GEOMETRY
Point: 是
Multipoint: 是
Linestring: 是
Multilinestring: 是
Polygon: 是
Multipolygon: 是
GeometryCollection: 是

示例

以下示例显示了如何使用 STV_Extent。

返回线串的边界框，并验证它是否是有效的多边形：

=> SELECT ST_AsText(geom) AS bounding_box, ST_IsValid(geom)
   FROM (SELECT STV_Extent(ST_GeomFromText('LineString(0 0, 1 1)')) OVER() AS geom) AS g;
            bounding_box             | ST_IsValid
-------------------------------------+------------
 POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0)) | t
(1 row)

返回表中空间对象的边界框：

=> CREATE TABLE misc_geo_shapes (id IDENTITY, geom GEOMETRY);
CREATE TABLE
=> COPY misc_geo_shapes (gx FILLER LONG VARCHAR, geom AS ST_GeomFromText(gx)) FROM STDIN;
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> POINT(-71.03 42.37)
>> LINESTRING(-71.058849 42.367501, -71.062240 42.371276, -71.067938 42.371246)
>> POLYGON((-71.066030 42.380617, -71.055827 42.376734, -71.060811 42.376011, -71.066030 42.380617))
>> \\.
=> SELECT ST_AsText(geom_col) AS bounding_box
   FROM (SELECT STV_Extent(geom) OVER() AS geom_col FROM misc_geo_shapes) AS g;
                                                   bounding_box
------------------------------------------------------------------------------------------------------------------
 POLYGON ((-71.067938 42.367501, -71.03 42.367501, -71.03 42.380617, -71.067938 42.380617, -71.067938 42.367501))
(1 row)