Dependency

Dependency refers to the relationship of an attribute with the primary key of a table.

To say that an attribute is dependent on the primary key means that, given a particular value for the primary key, there is only one corresponding value for that attribute.

An attribute may be either directly or indirectly dependent on the primary key.

A directly dependent attribute depends on the value of the primary key itself. An indirectly dependent attribute depends on the value of another attribute, which is itself dependent on the primary key. This indirect dependency is sometimes called transitive dependency.

The concept of dependency is further explained with the example tables provided later in this information. See especially Second normal form.