Chapter 11, SQL/MM – A Basis for Cross-platform, Inter-operable, and Reusable SQL introduced the Oracle MDSYS
ST_GEOMETRY type hierarchy. In that chapter, the Oracle
TREAT operator was required to ensure that a subtype object such as a point, when created by the
GET_WKT method, was correctly understood to be an instance of that subtype (that is,
ST_POINT), so that the methods particular to its subtype (for example,
ST_X) can be called. This appendix examines the need for
TREAT in more detail.
ST_GEOMETRY hierarchy, a
POINT object can be created in the following two ways:
MDSYS.ST_GEOMETRY.FROM_WKT('POINT(6012578.005 2116495.361)',2872) ...