Olap_hierarchy.gif shows a crosstab of Sales SUM data. The outer row labels are years (1998 and 1999). Inner row labels are for Quarters: Q1, Q2, Q3, and Q4 for each year. Sales SUM is the only column, and it holds Sales totals for each of the eight quarters: Q1 1998, Q2, 1998, Q3 1998, and Q4 1998, Q1 1999, Q2 1999, Q3 1999, and Q4 1999.