SQL Queries for Mere Mortals: A Hands-On Guide to Data Manipulation in SQL, 4th Edition

13Grouping Data

“Don’t drown yourself with details. Look at the whole.”

—MARSHAL FERDINAND FOCH COMMANDER-IN-CHIEF, ALLIED ARMIES IN FRANCE

Topics Covered in This Chapter

Why Group Data?

The GROUP BY Clause

“Some Restrictions Apply”

Uses for GROUP BY

Sample Statements

Summary

Problems for You to Solve

Chapter 12, “Simple Totals,” explained how to use the aggregate functions (COUNT, MIN, MAX, AVG, and SUM) to ask SQL to calculate a value across all the rows in the table defined in your FROM and WHERE clauses. I pointed out, however, that after you include any value expression that contains an aggregate function in your SELECT clause, all your value expressions must either be a literal constant or contain an aggregate function. This characteristic ...