Database Glossary – N
Useful Terms For Working With Data

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

N

National Change of Address – NCOA

A USPS service that helps reduce database errors and undeliverable mail from mailing lists.

Negation

Specifying that a query is to select all records except those that have a particular value for a given field. Such queries are often unsafe, and many databases do not support negation.

Nested Query

See: Query, Nested.

Normal Form

1) A condition of tables and databases intended to reduce data redundancy and improve performance.

2) Rules and processes for putting tables and databases into normal form.

Normalization

1) The process of breaking up a table into multiple tables, each of which has a single theme, thereby reducing data redundancy.

2) The technique that reduces or eliminates the possibility that a database is subject to modification anomalies.

See also: Data Redundancy.

Null; Null Value

If a field contains a data item, that has a specific value. A field that does not contain a data item is said to have a null value. In a numeric field, a null value is not the same as a value of zero; in a character field, a null value is not the same as a blank — both the numeric zero and blank character are definite values. A null value indicates that the that the field’s value is undefined — it’s value is not known.