Denormalization is the process of selectively violating normalization rules and reintroducing redundancy into the model (and therefore, the database). This extra redundancy can reduce data retrieval time, which is the primary reason for denormalizing. We can also denormalize to create a more user-friendly model. For example, we might decide to denormalize company information into an entity containing employee information, because usually when employee information is retrieved, company information is also retrieved.

There are a number of different ways to denormalize. In this section, well discuss the two most common:

·         Rolldown denormalization

·         Rollup denormalization.

We will apply these two techniques to the ...

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