Structuring Database for Accounting

(ii) Single-valued vs. Multi-valued Attributes : An attribute with a single value for an entity is single-valued as opposed to those which multiple values. For example, height of a person is single-valued attribute while qualifications of that person are a multi-valued attribute. (iii) Stored vs.

Derived Attributes : Two or more attributes may be related in such a way that one or more becomes basic while the other becomes dependent on that basic attribute. For example, date of birth of a person is a stored attribute while age of that person is derived attribute. (iv) Null Values : Absence of a data item is represented by a special value called null value. There are three situation which may require the use of null values When a particular attribute does not apply to an entity; Value of an attribute is unknown, although it exists; Unknown because it does not exist.

(v) Complex Attributes : The composite and multi-valued attributes may be nested (or grouped) to constitute complex ones. The parenthesis () are used for showing grouping of components of composite attributes. The braces {} are used for showing the multi-valued attributes In the context of the example on accounting reality, the following attributes