Polygons

Different Shapes

A geometry datatype in Oracle can be used to hold any imaginable real world shape.

The shapes are as you would think points, lines, compound lines, polygons and mixtures of all the items in the list. So a single geometry object can "contain" a polygon and lines and points. Though it is not a good idea to (mis)use the sdo_geometry datatype in this way. All of the shape primitives can be further extended from 2D to their 3D equivalents.

I have previously looked at points and will now look at polygons.

• A polygon encloses an area. In other words, its start and end points are the same.
• A polygon can contain other polygons which can be thought of as islands or lakes which in turn can contain polygons ad infinitum.
• A polygon can be optimised by two points (rectangle) or three points (circle).
• The "sides"of a polygon cannot cross. Self crossing lines are valid. It is allowable to split such a geometry into self contained polygons that when viewed together look like a self crossing polygon.
• A polygon can be made up of any combination of compound linestrings.

There are many more rules that cover what is and isn't a valid polygon in the oracle documentation.