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	Issue TOC Print full article Print this page Download as PDF E-Mail this URL Flame the author     In this article Introduction Information Dissemination Products Reviewed How We Tested Data Clean and Normal Report Card

Normalizing data is an important part of database design. And cleaning data is critical for effective analysis. Essentially, normalization is the process of removing duplicate tuples (a tuple is a collection of attributes). This procedure reduces database size and helps ensure data integrity. Notice that several cells in the non-normalized chart below contain the same value multiple times. To normalize this data, the values are removed and placed in a separate tableÑcommonly referred to as a lookup tableÑand then referenced from the original table.

When a data query is performed on the second set of tables, a join must be performed. Data residing in a data warehouse is often non-normalized because of the amount of data stored and the performance degradation resulting from joins across more than one table when dealing with excessively large data sets. The data used in testing was non-normalized.

Data Chart Click here to enlarge