improve

Author: digoal

201904/20190421_01.md

@@ -182,6 +182,35 @@ st_astext | POLYGON((120.080290328964 69.0017473017801,119.781778114247 69.00174
 ..............  
 ```  
 
+5、输入任意一个泰森多边形ID搜索与之相邻的泰森多边形。  
+  
+```
+select st_collect(tc.poy) 
+from tc, 
+  (select * from tc where id=80) t 
+where st_intersects(tc.poy, t.poy) 
+and GeometryType(ST_Intersection(tc.poy, t.poy)) <> 'POINT' 
+; 
+```
+  
+![pic](20190421_01_pic_008.jpg)  
+  
+只有一个点相邻也会认为相邻，所以需要使用GeometryType过滤.   
+  
+```
+digoal=# select st_intersects(poyx, poyy), GeometryType(ST_Intersection(poyx, poyy)) from 
+(values(
+  ST_MakePolygon(ST_GeomFromText('LINESTRING(1 2, 2 2, 2 3, 1 2)'))
+,
+  ST_MakePolygon(ST_GeomFromText('LINESTRING(2 2, 3 2, 3 3, 2 2)'))
+)) as t (poyx, poyy)
+;
+ st_intersects | geometrytype 
+---------------+--------------
+ t             | POINT
+(1 row)
+```
+  
 ## 参考  
 https://en.wikipedia.org/wiki/Voronoi_diagram