What are the disadvantages of normalizing a table in a database?

All databases tend to be normalized to some degree; in fact, a relational database almost must adhere to a minimum of 1NF to be useful. However, the more a database is normalized, the greater the impact of processing time of queries is likely to be. For one thing, higher levels of normalization results in larger numbers of decode tables and the like, requiring more table joins in retrieval queries and more referential integrity overhead.