LocateAlong takes a geometry object and a measure to return as a multipoint the set of points found at the measure.
Syntax
db2gse.LocateAlong(g db2gse.ST_Geometry, adistance Double)
Return type
db2gse.ST_Geometry
Examples
The following CREATE TABLE statement creates the LOCATEALONG_TEST table. LOCATEALONG_TEST has two columns: the GID column, which uniquely identifies each row, and the G1 geometry column, which stores sample geometry.
CREATE TABLE LOCATEALONG_TEST (gid integer, g1 db2gse.ST_Geometry)
The following INSERT statements insert two rows. The first is a multilinestring; the second is a multipoint.
INSERT INTO db2gse.LOCATEALONG_TEST VALUES(
1, db2gse.ST_MLineFromText('multilinestring m ((10.29 19.23 5,23.82 20.29 6,30.19 18.47
7,45.98 20.74 8),
(23.82 20.29 6,30.98 23.98 7,42.92 25.98 8))',
db2gse.coordref()..srid(0)))
INSERT INTO db2gse.LocateAlong_TEST VALUES(
2, db2gse.ST_MPointFromText('multipoint m (10.29 19.23 5,23.82 20.29 6,30.19 18.47 7,
45.98 20.74 8,23.82 20.29 6,30.98 23.98 7,42.92 25.98)',
db2gse.coordref()..srid(0)))
In the following SELECT statement and the corresponding result set, the LocateAlong function is directed to find points whose measure is 6.5. The first row returns a multipoint containing two points. However, the second row returned an empty point. For linear features (geometry with a dimension greater than 0), LocateAlong can interpolate the point; however, for multipoints, the target measure must match exactly.
SELECT gid, CAST(db2gse.ST_AsText(db2gse.LocateAlong (g1,6.5)) AS
varchar(96)) "Geometry"
FROM LOCATEALONG_TEST
GID Geometry
----------- --------------------------------------------------------------
1 MULTIPOINT M ( 27.01000000 19.38000000 6.50000000, 27.40000000
22.14000000 6.50000000)
2 POINT EMPTY
2 record(s) selected.
In the following SELECT statement and the corresponding result set, the LocateAlong function returns multipoints for both rows. The target measure of 7 matches the measures in both the multilinestring and multipoint source data.
SELECT gid,CAST(db2gse.ST_AsText(db2gse.LocateAlong (g1,7)) AS varchar(96)) "Geometry"
FROM LOCATEALONG_TEST
GID Geometry
----------- --------------------------------------------------------------
1 MULTIPOINT M ( 30.19000000 18.47000000 7.00000000, 30.98000000
23.98000000 7.00000000)
2 MULTIPOINT M ( 30.19000000 18.47000000 7.00000000, 30.98000000
23.98000000 7.00000000)
2 record(s) selected.