将一个 WKT(Well Known Text)转化为对应的多边形内存形式
ST_Polygon(wkt)
wkt
: 待转化的 WKT, 支持的数据类型为 VARCHAR
返回值的数据类型为 GEOMETRY
MySQL > SELECT ST_AsText(ST_Polygon("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))"));
+------------------------------------------------------------------+
| st_astext(st_polygon('POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))')) |
+------------------------------------------------------------------+
| POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0)) |
+------------------------------------------------------------------+