Processing More Complex Queries

The query processing techniques studied in the previous chapter can be considered fundamental. In recent research, however, several more complex extensions have been proposed, which consider additional aspects. In this chapter, we consider such extensions and present them in the same order as in the previous chapter. Therefore, we first describe extensions to range queries, next we consider extensions to nearest-neighbor queries, and finally we present extensions to spatial join queries. These queries require significant I/O and CPU cost, and therefore sophisticated methods have be applied to reduce processing cost. Finally, approximate query processing techniques are presented that sacrifice accuracy for better performance.