ST_Envelope toma um objeto de geometria e retorna seu quadro delimitador como uma geometria.
Sintaxe
db2gse.ST_Envelope(g db2gse.ST_Geometry)
Tipo de retorno
db2gse.ST_Geometry
Exemplos
A coluna GEOTYPE na tabela ENVELOPE_TEST armazena o nome da subclasse de geometria armazenada na coluna de geometria G1.
CREATE TABLE ENVELOPE_TEST (geotype varchar(20), g1 db2gse.ST_Geometry)
As seguintes instruções INSERT inserem cada subclasse de geometria na tabela 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)))
A seguinte instrução SELECT relaciona o nome da subclasse ao lado de seu envelope. Como a função ST_Envelope retorna um ponto, uma cadeia de linha ou um polígono, sua saída será convertida em texto com a função ST_AsText. A função CAST converte o resultado padrão varchar(4000) da função ST_AsText para um varchar(280).
SELECT GEOTYPE, CAST(db2gse.ST_AsText(db2gse.ST_Envelope(g1)) AS varchar(280)) "The envelope" FROM ENVELOPE_TEST
O seguinte conjunto de resultados retorna.
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.