Chapter 4. Restricting, Sorting, and Grouping Data

Unless your database tables are very small, or your data reporting needs are very limited, you will want to restrict the rows returned from your queries. In cases where you want to see the results of the queries in a particular order, you will want to sort the results. Grouping the data—for example, grouping sales figures by month, salary totals by department, and so forth—can be done in conjunction with restricting and sorting the data in a SQL statement.

Scott's widget company has been growing by leaps and bounds over the past few months, and it has expanded to international locations. While Scott has enjoyed being the data analyst and DBA, he has turned over these roles to Janice. The employee-related database tables have been redesigned and turned over to the HR department. All of our examples from this point on will use the HR schema, which contains the following tables: COUNTRIES, DEPARTMENTS, EMPLOYEES, JOBS, JOB_HISTORY, LOCATIONS, and REGIONS. The names of these tables should be self-explanatory.