Sams Teach Yourself SQL in 21 Days, Fourth Edition

Day 5

Quiz

1:	When performing aggregate functions (SUM(column_name)) must you group on any nonaggregate columns in your select statement?
A1:	Yes, when using aggregate functions in a query, all columns that are not associated with aggregate functions must be listed in the GROUP BY clause.
2:	What is the function of the GROUP BY clause, and what other clause does it act like?
A2:	The GROUP BY clause groups data result sets that have been manipulated by various functions. The GROUP BY clause acts like the ORDER BY clause in that it orders the results of the query in the order the columns are listed in the GROUP BY.
3:	Will this SELECT work? SQL> SELECT NAME, AVG(SALARY), DEPARTMENT FROM PAY_TBL WHERE DEPARTMENT = 'ACCOUNTING' ORDER BY NAME GROUP BY ...