PROC SQL allows a subquery (contained in parentheses) at any point in an expression where a simple column value or constant can be used. In this case, a subquery must return a single value, that is, ...

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 ...

What is window function vs subquery in SQL? In summary, subqueries and window functions are used for different purposes in SQL, and each has its strengths and weaknesses.