postgresql基于postgis常用空间函数

1、st_astext 空间二进制转文本
select st_astext(geo) from

2、ST_AsGeoJSON 空间数据转geojson格式
select ST_AsGeoJSON(geom) from

3、ST_Transform 坐标转换
select st_transform(geom,3857) from mytable

4、st_srid 查询数据表坐标系
select st_srid(geom) from mytable

5、ST_GeomFromText 文本转二进制
select ST_GeomFromText('POINT(119.976900368929 31.8078044056892)',3857)

6、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))

7、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 mytable where xzqhcode='340103009'),0)

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

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

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

11、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  mytable  order by distance asc  limit 5

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