PG+PostGIS 空间函数查询

1、计算线路长度（米）
SELECT patrolid, st_length(ST_Transform(geom,3857))
FROM public.patrolrecord where patrolid='3d4f8e0d-e759-469f-b78e-50f6445b56c9'

ST_Area(ST_Transform(geom,3857))

2、空间相交计算
判断点是否在面内：
select ST_DWithin(ST_SetSRID(ST_MakePoint(117.272031,31.868486),4326),(SELECT geom from sxkwg where xzqhcode='340103009'),0)

3、矩形查询
_st_intersects(st_transform(ST_MakeEnvelope(" + leftTopX + "," + leftTopY + "," + rightBottomX + "," + rightBottomY + ",4326" + "),4326),geom)

4、多边形查询
SELECT gid,year,cc,gb,ec,name,type,cc,gb,ec,name,type,st_astext(geom) wkt FROM V_ARCP where ST_Intersects(st_geometryfromtext('wkt',4326), geom) and year='2017'

5、根据已存在经纬度字段更新geometry字段
update map_thematicinfo set geom =ST_SetSRID(ST_MakePoint(longitude,altitude),4326) where gid=138

6、查询两点之间的距离（获取面状要素几何中心）
select jdm,st_distance(ST_Centroid(geom),ST_GeomFromText('POINT(117.12927656982 31.9223723088035)',4326),true) as distance from jzw order by distance asc limit 5

7、合并多个几何对象
update tb_duty_area set geom=SELECT st_union(geom) from tb_duty_area where (uid=49 or uid =107) WHERE uid=363