N

nested table expression

A fullselect in a FROM clause (surrounded by parentheses).

nonleaf page

A page that contains keys and page numbers of other pages in the index (either leaf or nonleaf pages). Nonleaf pages never point to actual data.

nonpartitioned index

An index that is not physically partitioned. Both partitioning indexes and secondary indexes can be nonpartitioned.

nonpartitioned secondary index

An index on a partitioned table space that is not the partitioning index and is not partitioned.

nonscrollable cursor

A cursor that can be moved only in a forward direction. Nonscrollable cursors are sometimes called forward-only cursors or serial cursors.

normalization

A key step in the task of building a logical relational database design. Normalization helps avoid redundancies and inconsistencies in data. An entity is normalized if it meets a set of constraints for a particular normal form (first normal form, second normal form, and so on). Contrast with denormalization.

NPSI

Nonpartitioned secondary index.

null

A special value that indicates the absence of information.

NULLIF

A scalar function that evaluates two passed expressions, returning either NULL if the arguments are equal or the value of the first argument if they are not.