In this chapter you will learn to
• 051.5.1 Identify the Available Group Functions
• 051.5.2 Describe the Use of Group Functions
• 051.5.3 Group Data by Using the GROUP BY Clause
• 051.5.4 Include or Exclude Grouped Rows by Using the HAVING Clause
Single-row functions, explored in Chapter 10, return a single value for each row in a set of results. Group or aggregate functions operate on multiple rows. They are used to count the number of rows or to find the average of specific column values in a dataset. Many statistical operations, such as calculating standard deviation, medians, and averages, depend on executing functions against grouped data and not just single rows.
You will examine group functions ...