Creating an own object-relational function.

Question

Hi
I'd like to create a new function on a object-relational datatype. Where can I find information about comparable methods like SDO_AREA and how to build an own.
Thanks
Chris

Answer 1

You can use PL/SQL to write such functions.
I have written many functions that operates on SDO_Geometry objects.
This exampla calculates the minimal bounding rectangle of a sdo_geometry:
FUNCTION Calc_mbr( Geo Mdsys.Sdo_geometry )
RETURN VARCHAR2 IS
Resultat VARCHAR2( 100 );
Antelem NUMBER;
Antord NUMBER;
X1 NUMBER;
Y1 NUMBER;
X2 NUMBER;
Y2 NUMBER;
X NUMBER;
Y NUMBER;
E NUMBER;
C NUMBER;
Startingoffset NUMBER;
Startingoffsetnext NUMBER;
Etype NUMBER;
Interpretation NUMBER;
BEGIN
Resultat := NULL;
IF NOT Geo.Sdo_point IS NULL THEN
Resultat :=
TO_CHAR( Geo.Sdo_point.Y ) || ';' || TO_CHAR( Geo.Sdo_point.X ) || ';' ||
TO_CHAR( Geo.Sdo_point.Y ) ||
';' ||
TO_CHAR( Geo.Sdo_point.X ) ||
RETURN Resultat;
END IF;
IF Geo IS NOT NULL THEN
Antelem := Geo.Sdo_elem_info.COUNT( );
Antord := Geo.Sdo_ordinates.COUNT( );
E := 1;
WHILE E < Antelem LOOP
Startingoffset := Geo.Sdo_elem_info( E );
Etype := Geo.Sdo_elem_info( E + 1 );
Interpretation := Geo.Sdo_elem_info( E + 2 );
IF ( Antelem > E * 3 ) THEN
Startingoffsetnext := Geo.Sdo_elem_info( E + 3 );
--Start of ordinates for next element
ELSE
Startingoffsetnext := Antord + 1;
END IF;
IF Etype > 0 THEN
IF ( E = 1 ) THEN -- initalization .
X1 := Geo.Sdo_ordinates( 1 );
X2 := X1;
Y1 := Geo.Sdo_ordinates( 2 );
Y2 := Y1;
END IF;
C := Startingoffset;
WHILE C < Startingoffsetnext LOOP
X := Geo.Sdo_ordinates( C );
Y := Geo.Sdo_ordinates( C + 1 );
IF X < X1 THEN
X1 := X;
ELSIF X > X2 THEN
X2 := X;
END IF;
IF Y < Y1 THEN
Y1 := Y;
ELSIF Y > Y2 THEN
Y2 := Y;
END IF;
C := C + 4; -- x,y,z,m
END LOOP;
END IF;
E := E + 3; -- Elements are always triplets.
END LOOP;
Resultat :=
TO_CHAR( Y1 ) || ';' || TO_CHAR( X1 ) || ';' || TO_CHAR( Y2 ) || ';' ||
TO_CHAR( X2 ) ||
ELSE
Resultat := NULL;
END IF;
RETURN Resultat;
END;