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High Quality Content by WIKIPEDIA articles! Data redundancy occurs in database systems which have a field that is repeated in two or more tables. For instance, in case when customer data is duplicated and attached with each product bought then redundancy of data is a known source of inconsistency, since customer might appear with different values for given attribute. Data redundancy leads to data anomalies and corruption and generally should be avoided by design.Database normalization prevents redundancy and makes the best possible usage of storage. Proper use of foreign keys can minimize data redundancy and chance of destructive anomalies. However sometimes concerns of efficiency and convenience can result redundant data design despite the risk of corrupting the data.