使用與參考手冊

ST_Envelope

ST_Envelope 使用一個幾何物件並傳回它的外框作為幾何。

語法

db2gse.ST_Envelope(g db2gse.ST_Geometry)

回覆類型

db2gse.ST_Geometry

範例

ENVELOPE_TEST 表格中的 GEOTYPE 直欄儲存的幾何次類別名稱原本是儲存在 G1 幾何直欄。

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

下列 INSERT 陳述式將每一個幾何次類別插入 ENVELOPE_TEST 表格。

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)))

下列 SELECT 陳述式在次類別的包封旁邊列示次類別名稱。 因為 ST_Envelope 函數傳回點、線串或多邊形, 所以會使用 ST_AsText 函數將它的輸出轉換成文字。 CAST 函數將 ST_AsText 函數的預設 varchar(4000) 結果轉換成 varchar(280)。

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

傳回下列結果集。

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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