CODEWITHSUNDEEP
oracle-databaseclippolygonsoracle-spatial
Nathan
Nathan

Reputation: 77

Clipping a polygon in Oracle

I have a polygon in table 2 with its id, no and geometry. In table 1 I have polygons with the same fields. The polygon in table2 in intersects with a few polygons from table 1.What I am trying to do is clip of the polygons which overlap polygon from table 2 and insert the same fields and geometry in table 3. So if polygon from table 2 has 2 overlaps I want to get rid of those overlaps and just get the rest into a new table.The following code is for returning the clipped part of the geometry .How do I get the geometry for the polygon after the clipping is done.

insert into table 3  
select a.store_id,b.store_id,a.store_number,a.client_id,sdo_geom.sdo_intersection(b.geometry,a.geometry,0.005)  
from table_1 a, table_2 b  
where b.store_id=34746  
and sdo_anyinteract(b.geometry,a.geometry)='True';

Upvotes: 1

Views: 1615

Answers (2)

Greg Braswell
Greg Braswell

Reputation: 143

I think you're trying to clip a single geometry with multiple geometries? sdo_difference only allows 1(single) geometry entity to clip another (single) geometry entity.

I have a similar requirement and solved it with sdo_aggr_union. This is now a part of Oracle Locator in 12c. 

    with minisegs as (
    SELECT seg.seg_cnn cnn,SDO_GEOM.SDO_DIFFERENCE(seg.shape,(
        select SDO_AGGR_UNION(SDOAGGRTYPE(node.geometry, 0.005))
        from node_poly node 
        where SDO_RELATE(node.geometry,seg.shape,  'mask = anyinteract') = 'TRUE')) geom
    from mv_act_segs seg) 
 select cnn,sdo_geom.sdo_length(geom,0.01) len, geom from minisegs
    where geom is not null 
    and sdo_geom.sdo_length(geom,0.01)>5

this is clipping a line segment node(point) buffers on both ends. In this case I needed to create a single geometry object from multiple objects for the sdo_difference to work. for subsequent process I needed to filter out short/null segments.

Upvotes: 1

Ben
Ben

Reputation: 1927

Instead of using sdo_geom.sdo_intersection, you probably want to use sdo_geom.sdo_difference - this acts as a minus operation:

enter image description here

Upvotes: 1

Related Questions