………is a special field value, distinct from 0, blank or any other value, that indicates that the value for the field is missing or otherwise unknown.

If there are no functional dependencies between two (or more) non-primary key attributes, this describes …………

A/an ……..can shield electronic equipment from power spikes.

Hierarchical databases do not use ………… as relational databases do for searching procedures

The foreign key is not necessarily the …….. in its current table.

The database management software creates and reads the data dictionary to ascertain what ……… exist and checks to see if specific users have the proper access right to view them.