A database is an organized collection of related data. Not all data needs to be handled in a database, but you need a database when are facing one of these problems:

• Data difficult to handle because of size and speed
• Multiple users updating the data
• Redundant values
• Lack of accuracy
• Lack of security

To store and manage your database you use a Database Management System (DBMS), a software designed to:

• Define, modify, and query a database
• Control user access
• Permit concurrent access
• Maintain integrity
• Provide loading, backup, and recovery of data
• Support additional data management functions

Common DBMS are MySQL, MS SQL Server and Oracle database. MS Access is also a DBMS, but it is designed to handle data locally.

In this section you will find data modeling techniques used to design databases, starting with the entity-relationship model. You will also find how to do the main operations in databases using SQL, the standard language to handle databases. Finally you will see how to perform queries on databases using SQL.