GROUP BY clause is a venerable member of the SQL statement family. After learning basic
SELECT statements, it is one of first specialized parts of SQL that many practitioners cut their teeth on when learning to create aggregations from raw data and transform that data into useful information.
Before I get too deeply into the use of
GROUP BY, this would be a good time provide some information about the test environment. All SQL in this chapter was prepared using the Oracle 220.127.116.11 64 bit version on Windows 7. The database account I used has DBA privileges. Using an account with DBA privileges simplifies the use of
dbms_xplan.display_cursor, using data from other accounts, and selecting data from system ...