- By Itzik Ben-Gan
This chapter introduced the concept of windowing in SQL. It provided the background to window functions, explaining the motivation for their use. The chapter then provided a glimpse of solving querying tasks using window functions by addressing the task of identifying ranges of existing values in a sequence—a problem also known as identifying islands. The chapter then proceeded to explain the design of window functions, covering the elements involved in window specifications: partitioning, ordering, and framing. Finally, this chapter explained how the SQL standard addresses the need to reuse a window specification or part of it. The next chapter provides a breakdown of window functions and gets into more detail.