ST_ASTEXT

描述

将一个几何图形转换为 WKT (Well-Known Text) 文本表示形式。WKT 是一种用于表示地理空间数据的文本格式，广泛应用于地理信息系统 (GIS) 中。

目前支持的几何图形类型包括：Point（点）、LineString（线）、Polygon（多边形）、MultiPolygon（多多边形），Circle(圆)

别名

• ST_ASWKT

语法

ST_ASTEXT( <geo>)

参数

参数	说明
<geo>	需要转换为 WKT 格式的几何图形对象

返回值

该几何图形的 WKT 表示形式 ST_ASTEXT 存在以下边缘情况：

• 若输入参数为 NULL，返回 NULL。

举例

点对象转换

SELECT ST_AsText(ST_Point(24.7, 56.7));

+---------------------------------+
| st_astext(st_point(24.7, 56.7)) |
+---------------------------------+
| POINT (24.7 56.7)               |
+---------------------------------+

线对象转换

mysql> SELECT ST_AsText(ST_GeometryFromText("LINESTRING (1 1, 2 2)"));
+---------------------------------------------------------+
| ST_AsText(ST_GeometryFromText("LINESTRING (1 1, 2 2)")) |
+---------------------------------------------------------+
| LINESTRING (1 1, 2 2)                                   |
+---------------------------------------------------------+

多边形对象转换

mysql> SELECT ST_AsText(ST_Polygon("POLYGON ((114.104486 22.547119,114.093758 22.547753,114.096504 22.532057,114.104229 22.539826,114.106203 22.542680,114.104486 22.547119))"));
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| ST_AsText(ST_Polygon("POLYGON ((114.104486 22.547119,114.093758 22.547753,114.096504 22.532057,114.104229 22.539826,114.106203 22.542680,114.104486 22.547119))")) |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| POLYGON ((114.104486 22.547119, 114.093758 22.547753, 114.096504 22.532057, 114.104229 22.539826, 114.106203 22.54268, 114.104486 22.547119))                      |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+

多多边形对象转换

mysql> SELECT ST_AsText(ST_GeometryFromText("MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)), ((2 2, 3 2, 3 3, 2 3, 2 2)))"));
+-----------------------------------------------------------------------------------------------------------+
| ST_AsText(ST_GeometryFromText("MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)), ((2 2, 3 2, 3 3, 2 3, 2 2)))")) |
+-----------------------------------------------------------------------------------------------------------+
| MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)), ((2 2, 3 2, 3 3, 2 3, 2 2)))                                   |
+-----------------------------------------------------------------------------------------------------------+

圆的对象转换

mysql> SELECT ST_AsText(ST_Circle(116.39748, 39.90882, 0.5));
+------------------------------------------------+
| ST_AsText(ST_Circle(116.39748, 39.90882, 0.5)) |
+------------------------------------------------+
| CIRCLE ((116.39748 39.90882), 0.5)             |
+------------------------------------------------+

NULL 输入

mysql> SELECT ST_AsText(NULL);
+-----------------+
| ST_AsText(NULL) |
+-----------------+
| NULL            |
+-----------------+