Database management systems allow users to store bits of information, organize it and retrieve some or all of it as needed. Each of the main types of database management systems requires a software program that creates records to organize the data and creates reports from that data. The software programs for databases create one of four common types: hierarchical databases, network databases, relational databases or object-oriented databases.
The hierarchical database is one of the oldest types of database management systems. It is most commonly used on mainframe computers. The database creator pre-defines the relationships between each record and its data. The structure requires a root record, or parent, from which the database designer creates a parent-child relationship for each bit of data that goes into the database.
A network database also organizes data by using defined parent-child relationships. Like a real family, the network database structure allows a piece of data classified as a child to have more than one parent. This is an improvement over hierarchical types of database management systems. It allows users to connect information in one database to another set of data through the parent record and the child record.
The relational database management system has increased in popularity because of its flexibility and ease of use. It allows the database designer to use individual pieces of information to create relationships between separate databases without the restriction of parent or owner relationships. The information in one database that ties it to data in a different one is a unique identifier, such as an employee identification number.
Relational databases management systems allow database designers to create one database to store payroll and salary information for employees. The designer creates a separate database for personal information such as home addresses and phone numbers. Different users might input and update the records in each database. Reports pull data from the records of any database in which the matching employee identification number is found.
Object-oriented types of database management systems provide a way to organize data other than numbers and text. Designers use them to accommodate multimedia items such as photos, music and videos. This database management system uses two identifiers for each item. The first is a descriptive object name, and the second is a miniature program with instructions or methods that the computer runs during storage and retrieval. The two parts become an object that the database users can organize like they can with text or numbers.