2.7.3 Compound Line String

Figure 2-5 illustrates a crescent-shaped object represented as a compound line string made up of one straight line segment and one circular arc. Four points are required to represent this shape: points (10,10) and (10,14) describe the straight line segment, and points (10,14), (6,10), and (14,10) describe the circular arc.

Figure 2-5 Compound Line String

Description of "Figure 2-5 Compound Line String"

In the SDO_GEOMETRY definition of the geometry illustrated in Figure 2-5:

• SDO_GTYPE = 2002. The first 2 indicates two-dimensional, and the second 2 indicates one or more line segments.

• SDO_SRID = NULL.

• SDO_POINT = NULL.

• SDO_ELEM_INFO = (1,4,2, 1,2,1, 3,2,2). There are three triplet elements: 1,4,2, 1,2,1, and 3,2,2.

  The first triplet indicates that this element is a compound line string made up of two subelement line strings, which are described with the next two triplets.

  The second triplet indicates that the line string is made up of straight line segments and that the ordinates for this line string start at offset 1. The end point of this line string is determined by the starting offset of the second line string, 3 in this instance.

  The third triplet indicates that the second line string is made up of circular arcs with ordinates starting at offset 3. The end point of this line string is determined by the starting offset of the next element or the current length of the SDO_ORDINATES array, if this is the last element.

• SDO_ORDINATES = (10,10, 10,14, 6,10, 14,10).

Example 2-8 shows a SQL statement that inserts the geometry illustrated in Figure 2-5 into the database.

INSERT INTO cola_markets VALUES(
  11,
  'compound_line_string',
  SDO_GEOMETRY(
    2002,
    NULL,
    NULL,
    SDO_ELEM_INFO_ARRAY(1,4,2, 1,2,1, 3,2,2), -- compound line string
    SDO_ORDINATE_ARRAY(10,10, 10,14, 6,10, 14,10)
  )
);