When it comes to data warehouse query performance, speed is everything. Faster performance means needed data and analysis is available to act upon ­ quickly. In order to achieve this goal, data warehouse experts agree that data aggregates can be a very powerful tool. According to Ralph Kimball, expert and author of The Data Warehouse Lifecycle Toolkit, data warehouse administrators can "expect anywhere from a tenfold to a thousandfold improvement in runtime performance by having the right aggregates available."

Aggregates are pre-stored summary records held in a data warehouse. They are usually built from the base layer upward, culminating in high-level totals. For example, a data warehouse administrator may decide to build aggregates for sales based on product, store and time-related totals such as month and year. Tables of aggregates eliminate the time and resources required to summarize data each time it is needed to respond to a query, allowing the query to be answered very efficiently in just a few seconds.

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