Guida di riferimento per l'utente

ST_Envelope

ST_Envelope rileva un oggetto di geometria e restituisce la casella di limite come geometria.

Sintassi

db2gse.ST_Envelope(g db2gse.ST_Geometry)

Tipo di ritorno

db2gse.ST_Geometry

Esempi

La colonna GEOTYPE della tabella ENVELOPE_TEST memorizza il nome della classe secondaria di geometria memorizzata nella colonna G1.

CREATE TABLE ENVELOPE_TEST (geotype varchar(20), g1 db2gse.ST_Geometry)

Le seguenti istruzioni INSERT inseriscono ogni classe secondaria di geometria nella tabella ENVELOPE_TEST.

INSERT INTO ENVELOPE_TEST
VALUES('Point',
       db2gse.ST_PointFromText('point (10.02 20.01)', 
      db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES ('Linestring',
        db2gse.ST_LineFromText('linestring (10.01 20.01, 10.01 30.01, 
        10.01 40.01)', db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES('Linestring',
       db2gse.ST_LineFromText('linestring  (10.02 20.01,10.32 23.98,11.92 25.64)',
       db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES('Polygon',
       db2gse.ST_PolyFromText('polygon ((10.02 20.01,11.92 35.64,25.02 34.15,
                               19.15 33.94,10.02 20.01))',
                    db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES('Multipoint',
       db2gse.ST_MPointFromText('multipoint (10.02 20.01,10.32 23.98,11.92 25.64)',
       db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES('Multilinestring',
       db2gse.ST_MLineFromText('multilinestring ((10.01 20.01,20.01 20.01,
       30.01 20.01), (30.01 20.01,40.01 20.01,50.01 20.01))',
                     db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES('Multilinestring',
       db2gse.ST_MLineFromText('multilinestring ((10.02 20.01,10.32 23.98,
       11.92 25.64), ( 9.55 23.75,15.36 30.11))',
                     db2gse.coordref()..srid(0)))
 
INSERT INTO ENVELOPE_TEST
VALUES('Multipolygon',
       db2gse.ST_MPolyFromText('multipolygon (((10.02 20.01,11.92 35.64,
       25.02 34.15, 19.15 33.94,10.02 20.01)),
                                    ((51.71 21.73,73.36 27.04,71.52 32.87,
                                      52.43 31.90,51.71 21.73)))',
                     db2gse.coordref()..srid(0))) 

L'istruzione SELECT elenca il nome della classe secondaria accanto al relativo inviluppo. Poiché la funzione ST_Envelope restituisce un punto, una stringa lineare o un poligono, l'output viene convertito in testo dalla funzione ST_AsText. La funzione CAST viene utilizzata per ridurre il valore predefinito varchar(4000) della funzione ST_AsText in varchar(280).

SELECT GEOTYPE, CAST(db2gse.ST_AsText(db2gse.ST_Envelope(g1)) AS varchar(280)) 
"The envelope"
FROM ENVELOPE_TEST

Viene restituita la seguente serie di risultati.

GEOTYPE              The envelope
-------------------- ----------------------------------------------------------
Point                POINT ( 10.02000000 20.01000000)
Linestring           LINESTRING ( 10.01000000 20.01000000, 10.01000000
 40.01000000)
Linestring           POLYGON (( 10.02000000 20.01000000, 11.92000000
 20.01000000, 11.92000000 25.64000000, 10.02000000 25.64000000, 10.02000000
 20.01000000))
Polygon              POLYGON (( 10.02000000 20.01000000, 25.02000000
 20.01000000, 25.02000000 35.64000000, 10.02000000 35.64000000, 10.02000000
 20.01000000))
Multipoint           POLYGON (( 10.02000000 20.01000000, 11.92000000
 20.01000000, 11.92000000 25.64000000, 10.02000000 25.64000000, 10.02000000
 20.01000000))
Multilinestring      LINESTRING ( 10.01000000 20.01000000, 50.01000000
 20.01000000)
Multilinestring      POLYGON (( 9.55000000 20.01000000, 15.36000000
 20.01000000, 15.36000000 30.11000000, 9.55000000 30.11000000, 9.55000000
 20.01000000))
Multipolygon         POLYGON (( 10.02000000 20.01000000, 73.36000000
 20.01000000, 73.36000000 35.64000000, 10.02000000 35.64000000, 10.02000000
 20.01000000))
 
  8 record(s) selected.


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