基于postGIS的第二个成功应用

1)select c."簇编号", c.cityname , c."面积", count(d.cgi) "小区数" , sum(d.upoctdl+d.upoctul)/1000000 "总流量kB" , sum(d.upoctdl+d.upoctul)/c."面积"/1000000 "平均流量KB/sqkm"
from
(select a.*, b.*  from eutrancelltdd_cm a , grid_region b where st_contains(b.geom, a.point) and a.scan_start_time = timestamp '2015-2-22 00:00') c
left join eutrancelltdd_pm_1_dd d on c.scan_start_time = d.scan_start_time and c.cgi = d.cgi
group by c."簇编号",c.cityname, c."面积"


2)http://wenku.baidu.com/view/8f9e852b7375a417866f8fab.html