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

Summary

We began the chapter by explaining to you why you might want to group data to get multiple subtotals from a result set. After tantalizing you with an example, we proceeded to show how to use the GROUP BY clause to solve the example problem and several others. We also showed how to mix column expressions with aggregate functions.

We next explored an interesting example of using GROUP BY in a subquery that acts as a filter in a WHERE clause. We subsequently pointed out that constructing a query using GROUP BY and no aggregate functions is the same as using DISTINCT in your SELECT clause. Then we warned you to carefully construct your GROUP BY clause to include the columns and not the expressions.

We wrapped up our discussion of the GROUP ...