SAS Certified Professional Prep Guide

Using Natural Joins

A Brief Overview

A natural join automatically selects columns from each table to match rows. With a natural join, PROC SQL identifies columns in each table that have the same name and type, and uses those as the join criteria. The advantage of using a natural join is that the coding is streamlined. The ON clause is implied, and you do not need to use table aliases to qualify column names that are common to both tables.

If you specify a natural join on tables that do not have at least one column with a common name and type, the result is a Cartesian product. You can use a WHERE clause to limit the output. Because the natural join makes certain assumptions about what you want to accomplish, you should examine your data ...