The outer PROC SQL query retrieves data from the view descriptor; the subquery uses a Pass-Through query to retrieve data. This query returns the names of employees who earn less than the average ...

Read this SQL tutorial to learn when to use SELECT, JOIN, subselects and UNION to access multiple tables with a single statement.

That expression closely resembles the expression I used in the WHERE clause in the first example. Since there are two ways to accomplish the same kind of query, which should you use?