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

Summary

We began this chapter by introducing you to aggregate functions. You learned that there are six different functions and that you can use them in the SELECT and WHERE clauses of a SELECT statement. You also learned that each aggregate function—except COUNT(*)—disregards all Null values as it performs its operation.

Next we showed how to use each aggregate function. You learned how to count rows or values with the COUNT functions, how to find the largest and smallest values with the MAX and MIN functions, how to calculate a mean average with the AVG function, and how to total a set of values with the SUM function. We also showed how to use the DISTINCT option with each function and explained that DISTINCT has no effect on the MAX and MIN ...