Improving Subtotal Calculation

If you have data that varies across dimensions such as date or place, you may need to determine how the data varies in each dimension. ROLLUP and CUBE are extension to the GROUP BY operator that allow you to use one query to compute data using multiple levels of grouping, instead of a separate query for each level.

• ROLLUP
  ROLLUP is an extension to the GROUP BY operator that calculates multiple levels of subtotals across a specified group of dimensions, and calculates a grand total, ROLLUP. Subtotals “roll up” from the most detailed level to the grand total.
• Cube
  CUBE is an extension to the GROUP BY operator that analyzes data by forming the data into groups in more than one dimension.