查看道路分級如下：

mapdb=# select distinct pathclass from rbeijing;
 pathclass
-----------
 0
 15
 2
 3
 4
(5 rows)

使用子查詢實現道路分級

  CONNECTIONTYPE postgis
  PROCESSING "CLOST_CONNECTION=DEFER"
  CONNECTION "user=map password=postgres dbname=mapdb host=192.168.1.11 port=5432"
  DATA "the_geom from  (select * from rbeijing where pathclass='3') as subquery using unique gid USING SRID=4326"









分級前的查詢代碼
  CONNECTIONTYPE postgis
  PROCESSING "CLOST_CONNECTION=DEFER"
  CONNECTION "user=zhangyi password=postgres dbname=zydb host=192.168.10.166 port=5432"
  DATA "the_geom from rbeijing using unique gid USING SRID=4326"                                                  
  #DATA "the_geom from  (select * from rbeijing where pathclass='3') as subquery using unique gid USING SRID=4326"

分級前的效果







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