Topology In Oracle Spatial

 What is Topology in Oracle Spatial?

I suggest you watch the video below about this article.

Imagine you have a map with streets, parks, and buildings. Topology is like a rulebook that defines relationships between these things:

• Points (like a park's location)
• Lines (like roads or rivers)
• Areas (like a city block or a lake)

With topology, we can say:

• Roads connect at intersections.
• A park can't overlap a building.
• A lake must stay inside its boundary.

Using topology helps keep your data correct and makes spatial queries faster. For example:

• Find all parks next to a river.
• Check if two roads cross.
• Ensure no two buildings overlap.

How to Implement Topology in Oracle Spatial?

1) Create a Topology

A topology is like a container for your spatial data.

BEGIN
  SDO_TOPO.CREATE_TOPOLOGY(
    'CITY_TOPO',        -- Name of the topology
    'USER_SCHEMA',      -- Your database schema
    0.005,              -- Tolerance for geometric operations
    'GEOMETRY_TABLE');  -- Table to hold the spatial data
END;

2) Create Spatial Tables

You'll create tables for points, lines, and polygons.

-- Points (like intersections)
CREATE TABLE POINTS (
  ID NUMBER PRIMARY KEY,
  GEOM SDO_GEOMETRY
);

-- Lines (like streets)
CREATE TABLE LINES (
  ID NUMBER PRIMARY KEY,
  GEOM SDO_GEOMETRY
);

-- Polygons (like city blocks)
CREATE TABLE POLYGONS (
  ID NUMBER PRIMARY KEY,
  GEOM SDO_GEOMETRY
);

3) Add Data

Insert some data into your tables.

INSERT INTO POINTS VALUES (
  1, 
  SDO_GEOMETRY(2001, 8307, SDO_POINT_TYPE(10, 10, NULL), NULL, NULL)
);

INSERT INTO LINES VALUES (
  1, 
  SDO_GEOMETRY(2002, 8307, NULL, SDO_ELEM_INFO_ARRAY(1, 2, 1), 
               SDO_ORDINATE_ARRAY(10, 10, 20, 20))
);

INSERT INTO POLYGONS VALUES (
  1, 
  SDO_GEOMETRY(2003, 8307, NULL, SDO_ELEM_INFO_ARRAY(1, 1003, 1),
               SDO_ORDINATE_ARRAY(5, 5, 15, 5, 15, 15, 5, 15, 5, 5))
);

4) Build Topology

Load this data into your topology.

BEGIN
  SDO_TOPO.LOAD_TOPOLOGY_LAYER(
    'CITY_TOPO',
    'POINTS',
    'LINES',
    'POLYGONS'
  );
END;

5) Perform Topology Queries

You can now query relationships, like finding which points are inside polygons.

SELECT p.ID
FROM POINTS p, POLYGONS g
WHERE SDO_INSIDE(p.GEOM, g.GEOM) = 'TRUE';