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ST_ConvexHull

ST_ConvexHullÀº ±âÇÏÇÐ ¿ÀºêÁ§Æ®¸¦ ÃëÇØ º¼·Ï µ¤°³¸¦ ¸®ÅÏÇÕ´Ï´Ù.

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db2gse.ST_ConvexHull(g db2gse.ST_Geometry)

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db2gse.ST_Geometry

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ÀÌ ¿¹¿¡¼­´Â GEOTYPE°ú G1 µÎ °³ÀÇ Ä÷³ÀÌ ÀÖ´Â CONVEXHULL_TEST Å×À̺íÀ» ÀÛ¼ºÇÕ´Ï´Ù. GEOTYPE Ä÷³ÀÎ varchar(20)Àº ±âÇÏÇÐÀ¸·Î Á¤ÀÇµÈ G1¿¡ ÀúÀåµÈ ±âÇÏÇÐÀÇ ¼­ºêŬ·¡½º À̸§À» ÀúÀåÇÕ´Ï´Ù.

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

°¢ INSERT¹®Àº CONVEXHULL_TEST Å×ÀÌºí¿¡ °¢ ¼­ºêŬ·¡½º À¯ÇüÀÇ ±âÇÏÇÐÀ» »ðÀÔÇÕ´Ï´Ù.

INSERT INTO CONVEXHULL_TEST
VALUES('Point',
       db2gse.ST_PointFromText('point (10.02 20.01)',
db2gse.coordref()..srid(0)))
 
INSERT INTO CONVEXHULL_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 CONVEXHULL_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 CONVEXHULL_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 CONVEXHULL_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 CONVEXHULL_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)))

´ÙÀ½ÀÇ SELECT¹®Àº GEOTYPE Ä÷³ ¹× convex hull¿¡ ÀúÀåµÈ ¼­ºêŬ·¡½º À̸§À» ³ª¿­ÇÕ´Ï´Ù. ST_ConvexHull ÇÔ¼ö¿¡ ÀÇÇØ »ý¼ºµÈ º¼·Ïµ¤°³(convexhull)´Â ST_AsText ÇÔ¼ö¿¡ ÀÇÇØ ÅØ½ºÆ®·Î º¯È¯µË´Ï´Ù. ±×·± ´ÙÀ½, ÀÌ´Â ST_AsTextÀÇ ±âº» Ãâ·ÂÀÌ varchar(4000)À̹ǷΠvarchar(256)·Î ¹èÁ¤µË´Ï´Ù.

SELECT GEOTYPE, CAST(db2gse.ST_AsText(db2gse.ST_ConvexHull(G1))) 
as varchar(256) "The convexhull"
FROM CONVEXHULL_TEST


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