Types of Databases:

DBMS supports many types of databases. Databases can be classified according to the
1) number of users 2) database location 3) data usage 4) structure.

Number of Users	1)       Single User Database
	2)       Multi User (workgroup, enterprise)
Data Locations	1)       Centralized Database
	2)       Distributed Database
Data Usage	1)       Operational Database
	2)       Data warehouse
Data Structure	1)       Structured Database
	2)       Unstructured Database

1)       According to number of users:

a)       Single-user database: It supports only one user at a time. In other words, if user A is using the database, users B must wait until user A finishes. A single-user database that runs on a personal computer is called desktop database or personal database.

b)       Multi-user database: It supports multiple users to access the database simultaneously. In this type, the following two subtypes are found.

i)         Workgroup database: When the multiuser database supports a relatively small number of users (usually fewer than 50) or a specific department within an organization, it is called a workgroup database.

ii)       Enterprise database: When the database is used by the entire organization and supports many users (more than 50, usually hundreds) across many departments, the database is known as an enterprise database.

2)       According to data location:

a)       Centralized database: A database that supports data located at a single site is called a centralized database.

b)       Distributed database: A database that supports data distributed across several different sites is called a distributed database.  

3)       According to data usage:

a)       Operational database: A database that is designed primarily to support a company's day-to-day operations is classified as an operational database (also called transactional or production database). For example, transactions such as product sales and payments include day-to-day operations. Such transactions are recorded accurately and immediately by operational databases.

b)       Datawarehouse: A data warehouse focuses primarily on storing data used to generate information required to make tactical or strategic decisions. Such decisions typi­cally require extensive "data manipulation” to extract information to formulate pric­ing decisions, sales forecasts, market positioning, and so on. Most decision-support data are based on historical data obtained from operational databases, additionally, the data warehouse can store data derived from many sources.

4)       According to data structure:

a)       Unstructured database: Unstructured data are data that exist in their original (raw) state, that is, in the format in which they were collected. All the companies use unstructured data such as e-mails, memos, documents containing rules, Web pages and so on.

b)       Structured database: Structured data are the result of taking unstructured data and formatting such data to generate of information. We apply structure (format) based on the type of processing that we intend to perform on the data. Operational database is one example for structured database.

The following table compares features of different databases.

	NUMBER OF USERS			DATA LOCATION		DATA USAGE
Product	Single User	Multiuser Work-group	Multiuser Enterprise	Centralized	Distributed	Operational	Data Warehouse
MS-Access	P	P		P		P
SQL Server	P	P	P	P	P	P	P
DB2	P	P	P	P	P	P	P
MySQL	P	P	P	P	P	P	P
Oracle	P	P	P	P	P	P	P