Database Management

• a database is a repository of information and collection of tables that are related to each other.
• a computerized database allows you to create and manage your database much more efficiently and effectively than a manual database.
• a database management system is a software package designed to define, manipulate, retrieve and manage data in a database.
• a database management system generally manipulates the data itself, the data format, field names, record structure and file structure.
• a database management system also defines rules to validate and manipulate the data.
• examples of database management systems are MySQL, Microsoft Access, Oracle, PostgreSQL, dBASE, FoxPro, SQLite, and IBM D82.
• a database file is the entire database.
• a table is a collection of records made up of a set of rows and columns.
• a record is a collection of related fields. it contains a single row and many columns. it is also known as tuples.
• a field is a single column in a table that stores data. it is also known as an attribute.
• an entity is an item in the real world that is represented in a database.
• a primary key is a field that acts as a unique identifier for each record in a table.
• a candidate key is a field that could possibly act as the primary key for the table.
• a secondary or alternate key is a candidate key that has not been selected as a primary key.
• a composite key is a primary key that combines two or more fields together.
• a foreign key is a field in a table that has been linked with the primary key field of another table.