SAS Certification Prep Guide, 4th Edition

Chapter 4: Combining Tables Vertically Using PROC SQL

1. Correct answer: c

   In set operations that use the operator EXCEPT, INTERSECT, or UNION, and no keyword, columns are overlaid based on their position in the SELECT clause. It does not matter whether the overlaid columns have the same name. When columns are overlaid, the column name is taken from the first table that is specified in the SELECT clause.
2. Correct answer: d

   By default, when processing a set operation that contains the EXCEPT, INTERSECT, and UNION set operators, PROC SQL makes an extra pass through the data to eliminate duplicate rows. The keyword ALL is used to suppress that additional pass through the tables, allowing duplicate rows to appear in the result set. Because ...