Based on the conceptual structures, the database can be classified as follows:
- Flat- File database
- Relational database
- Hierarchical database
- Network database
- Object-Oriented database
Flat- File Database:
A database file that consists of single data table is a Flat-File database. Flat-file database can be quite useful for certain single-user or small-group situations, especially for maintaining lists such as address lists or inventories. Data that is stored, managed, and manipulated in spreadsheet is another example flat-file database.
Despite their simplicity, flat-file databases do have a significant limitation over databases consisting of multiple tables. They do not allow for more complex requests. This is fine if you merely need to locate a part or verify an address. However, very often you need to process more extensive information from multiple data tables which is not possible in flat-file databases.
A relational structure represents a database made up of a set of related tables. In a relational database, one or more common fields existing in two or more tables create a relationship between these tables. The common field or fields are called Keys.
A primary key is a key that uniquely identifies a record in a database table. In a relational databases, a primary key can consist of one or more fields. The relational database structure is the most prevalent database in today’s business organizations.
The hierarchical database structures were primarily used on Main Frame computers. In hierarchical databases, records are organized in a tree like structure by type. The relationship between record types is said to be a parent-child relationship, in which any child type relates only to a single parent type.
The Network database is very similar to the hierarchical structure except that any one record type can relate to any number of other record types.
Object oriented database:
An object oriented database is a newer structure that has been generating a great deal of interest in recent years. It represents very different approach to the way data is treated by database developers and users. The object oriented structure groups data items and their associated characteristics, attributes and procedures into complex items called objects. Physically an object can be anything: a product, or event, such as a house, an appliance, an art piece, a customer complaint, or even a purchase. An object is defined by its characteristics, attributes and procedures. An object’s characteristics can be text, sound, graphics and video. Examples of attributes might be color, size, style, quantity and price. A procedure refers to the processing or handling that can be associated to the object.