How to use SDO_GEOM.SDO_CLOSEST_POINTS as Query with Oracle Spatial - sql

Question

I am trying to use SDO_GEOM.SDO_CLOSEST_POINTS purely as a sql query. All the examples use it in conjunction with pl/sql. Is it possible to use it in a query without pl/sql and could anyone provide an example of the syntax for how to do that?
My specific task is trying to return the vertex on a line that is closest to a point.
http://docs.oracle.com/cd/B28359_01/appdev.111/b28400/sdo_objgeom.htm#SPATL1113
Thank you.

Answer 1

It's not possible to call a PL/SQL procedure from an SQL query.
I would suggest that you create an Oracle object type that wraps the OUT parameters from SDO_GEOM.SDO_CLOSEST_POINTS and then define your own PL/SQL function that calls the procedure that returns an instance of your object type.
Something like this:
CREATE TYPE closest_points_type AS OBJECT (
dist NUMBER
, geoma mdsys.sdo_geometry
, geomb mdsys.sdo_geometry
)
/
CREATE FUNCTION sdo_closest_points_sql (
p_geom1 IN sdo_geometry
, p_geom2 IN sdo_geometry
, p_tolerance IN NUMBER
, p_unit IN VARCHAR2
)
RETURN closest_points_type
IS
l_dist NUMBER;
l_geoma mdsys.sdo_geometry;
l_geomb mdsys.sdo_geometry;
BEGIN
sdo_geom.sdo_closest_points(
geom1 => p_geom1
, geom2 => p_geom2
, tolerance => p_tolerance
, unit => p_unit
, dist => l_dist
, geoma => l_geoma
, geomb => l_geomb
);
RETURN closest_points_type(l_dist, l_geoma, l_geomb);
END sdo_closest_points_sql;
/
You should then be able to call this function from a SELECT statement, and interrogate the resulting object like so:
WITH q1 AS (
SELECT
sdo_closest_points_sql(
mdsys.sdo_geometry(2002, NULL, NULL, sdo_elem_info_array(1,2,1), sdo_ordinate_array(1,1, 1,10, 1,20))
, mdsys.sdo_geometry(2002, NULL, NULL, sdo_elem_info_array(1,2,1), sdo_ordinate_array(2,5, 2,15, 2,25))
, 0.05
, NULL
) result
FROM dual
)
SELECT
(q1.result).dist dist
, (q1.result).geoma geoma
, (q1.result).geomb geomb
FROM q1