Physical Database Design

346 CHAPTER 15 Denormalization

would require a reorganization of the database schema and repopulation of

emp2, a potentially significant overhead.

In summary, the key effects of denormalization are:

1. A definite improvement (decrease) in query time.

2. A potential increase in update time.

3. A potential increase in storage space.

4. A potential loss of data integrity due to certain deletions.

5. The necessity for program transformations for all relevant queries.

6. The overhead needed to reorganize one or more tables (e.g., emp to emp2).

These effects require careful consideration. The example in Section 15.3 goes into more

details of this analysis.

Many database systems have software that provides data synchronization between

redundant data and base ...