Oracle SQL aggregate Geometries (Longitude, Latitude) - oracle

Question

I have this table
I wanted to sort by POS ASC and also aggregate the two columns X, and Y (so that these POINTS become a LINESTRING, EPSG:25832) so that my ID becomes Unique.
I don't have much experience with ORACLE SDO GEOMETRIES but with PostGIS.
Is there an easy way to do it? Since I didn't find any solution which worked correctly.
The output should be:
Any help maybe..? Thanks.

Answer 1

You can aggregate the coordinates into a string and convert it to an SDO_GEOMETRY type:
SELECT id,
SDO_GEOMETRY(
'LINESTRING(' || LISTAGG(x || ' ' || y, ',') WITHIN GROUP (ORDER BY pos) || ')'
) AS line
FROM table_name
GROUP BY id;
However, the string is limited to 4000 characters so it may fail if you have lots of coordinates.
If you just want the string (without converting it to an SDO_GEOMETRY) then remove the call to the SDO_GEOMETRY() constructor and just use LISTAGG on its own.
Alternately, you can generate the SDO_GEOMETRY object directly using UNPIVOT and CAST/COLLECT:
SELECT id,
SDO_GEOMETRY(
2002,
NULL,
NULL,
SDO_ELEM_INFO_ARRAY(1, 2, 1),
CAST(COLLECT(value ORDER BY pos, coord) AS SDO_ORDINATE_ARRAY)
)
FROM table_name t
UNPIVOT (value FOR coord IN (x AS 1, y AS 2))
GROUP BY id
If you want it as a WKT string then:
SELECT id,
SDO_GEOMETRY(
2002,
NULL,
NULL,
SDO_ELEM_INFO_ARRAY(1, 2, 1),
CAST(
COLLECT(value ORDER BY pos, coord)
AS SDO_ORDINATE_ARRAY
)
).get_WKT() AS wkt
FROM table_name t
UNPIVOT (value FOR coord IN (x AS 1, y AS 2))
GROUP BY id
Which, for the sample data, outputs:
ID
WKT
1
LINESTRING (362019.6 5693216.74, 361967.53 5693180.03)
2
LINESTRING (361993.564 5693198.385)
3
LINESTRING (361993.564 5693198.385)
fiddle
In Oracle 11g, if you just want the WKT string then you can create the types and function:
CREATE TYPE coord IS OBJECT(x NUMBER, y NUMBER)
/
CREATE TYPE coord_table IS TABLE OF coord
/
CREATE FUNCTION coords_to_wkt(
i_coords IN coord_table
) RETURN CLOB
IS
v_clob CLOB;
BEGIN
IF i_coords IS NULL OR i_coords.COUNT = 0 THEN
RETURN NULL;
END IF;
v_clob := 'LINESTRING(' || i_coords(1).x || ' ' || i_coords(1).y;
FOR i IN 2 .. i_coords.COUNT LOOP
v_clob := v_clob || ',' || i_coords(i).x || ' ' || i_coords(i).y;
END LOOP;
RETURN v_clob || ')';
END;
/
and use:
SELECT id,
coords_to_wkt( CAST( COLLECT( coord(x, y) ORDER BY pos ) AS coord_table ) ) AS wkt
FROM table_name
GROUP BY id;
fiddle