Ranking, framing, and windowing

In the previous section, we went through almost all aggregate functions, from the most popular, the SUM or AVG aggregates, to slightly more complicated aggregates, such as STDEV and VAR. Aggregate functions give an overview of statistical measures that are useful for further analysis and machine learning parameters. However, we often also need to sort or somehow compare data in an incoming dataset. For such purposes, T-SQL provides a set of ranking functions. The ranking function is a function that gives a numerical evaluation to each record in a dataset. Rankings always work over whole datasets or on parts of the dataset in a similar way to the grouping feature of aggregate queries, but without creating groups of typical aggregates. This feature, which is tightly bound to ranking, is called framing. In this section, we will learn about framing...