## Listen Software's How To: NormalizationJanuary 28, 2002 ## OverviewFollowing the normalization guidelines usually means splitting tables into two or more tables with fewer columns. Primary and foreign key relationships are designed into the new smaller tables, so they can be reconnected with a join operation. The advantage of splitting the table is to reduce data redundancy. Here's a brief guide to the standard normalization forms: ## First Normal FormAt each row and column intersections, there must be one and only one value. Each column in a row can have only one value, and that value must be atomic. ## Second Normal FormSecond normal form requires no non-key column be a fact about a subset of the primary key. Event non-key column must depend entirely on the entire primary key. The primary key must have an element of uniqueness. A primary key may be composed of one or more columns forming a unique key. The primary key does not change one created. The foreign key references an tables primary key. The primary to foreign key represents a one to many relationship. ## Third Normal FormThird Normal Forms Requires no non-key column depend on another non-key column. ## Fourth Normal FormFourth Normal form forbids independent one-to-may relationships between primary key columns and non-key columns. ## Fifth Normal FormFifth normal form breaks tables into the smallest possible pieces in order to eliminate all redundancy within a table. |