Each order number appears more than once. For example, order number 10100 appears four times. If you add a GROUP BY clause to the query, you can group the data by order number so that each order number appears only once:
Typically, you use a GROUP BY clause to perform an aggregation. For example, the following query returns order numbers and order totals. The Total column is an aggregate column. An aggregate column is a computed column that uses an aggregate function such as AVG, COUNT, MAX, MIN, or SUM.
Figure 2-31 shows the first 10 data rows returned by the information object query. The data is grouped by order number and the total for each order appears.
