Databases are very important part of many applications nowadays. Quite many applications needs to handle data. There is a need to save and edit the data and search some special information from the data. Databases makes those operations much more easier than example textfiles.

There are several kind of database types and this site is focused on Relational databases.

A database is an organized collection of data for one or more purposes, usually in digital form. The data is typically organized to model relevant aspects of reality. The database may contain, for example, hospital patient data or institution grades and course informations.

The term "database" refers both to the way its users view it, and to the logical and physical materialization of its data, content, in files, computer memory, and computer data storage. This definition is very general, and is independent of the technology used. However, not every collection of data is a database; the term database implies that the data is managed to some level of quality (measured in terms of accuracy, availability, usability, and resilience) and this in turn often implies the use of a general-purpose Database management system (DBMS).

Here are some common requirements for the database:

• No redundant data: we don't have to save the same data to several places
• We can search the data using several conditions
• Using the data and the applications which will use it are independent about the physical structure of the database

DBMS is typically a complex software system that meets many usage requirements, and the databases that it maintains are often large and complex. The utilization of databases is now spread to such a wide degree that virtually every technology and product relies on databases and DBMSs for its development and commercialization, or even may have such embedded in it. Also, organizations and companies, from small to large, heavily depend on databases for their operations.

Some of the most popular DBMS's:

• MySQL and MariaDB
• PostgreSQL
• SQL Server (Microsoft)
• Oracle

The three leading open source implementations are MySQL, PostgreSQL and SQLite.

DBS = Database + DBMS

Here is some examples of different kind of databases:

1. Hierarchical databases
2. Network databases
3. Relational databases (SQL databases)
4. Object-oriented databases
5. XML databases
6. NoSQL databases
7. Graph databases