Introduction To Database (Summary)

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(1) Data is distinct pieces of information, usually formatted in a special way. All software is divided into two general categories:data and programs. Programs are collections of instructions for manipulating data.

Data can exist in a variety of forms -- as numbers or text on pieces of paper, as bits and bytes stored in electronic memory, or as facts stored in a person's mind.

Strictly speaking, data is the plural of datum, a single piece of information. In practice, however, people use data as both the singular and plural form of the word.

(2) The term data is often used to distinguish binary machine-readable information from textual human-readable information. For example, some applications make a distinction between data files (files that contain binary data) and text files (files that contain ASCII data).

(3) In database management systems, data files are the files that store the database information, whereas other files, such as index files and data dictionaries, store administrative information, known as metadata.

Database

A database is simply an organized collection of related data, typically stored on disk, and accessible by possibly many concurrent users. Databases are generally separated into application areas. For example, one database may contain Human Resource (employee and payroll) data; another may contain sales data; another may contain accounting data; and so on. Databases are managed by a DBMS.

DBMS

A DBMS is responsible for:

• accessing data

• inserting, updating, and deleting data

• security

• integrity, facilitated by:

• locking

• logging

• application-defined rules, including triggers

• supporting batch and on-line programs

• facilitating backups and recoveries

• optimizing performance

• maximizing availability

• maintaining the catalog and directory of database objects

• managing the buffer pools

• acting as an interface to other systems programs

• supporting user interface packages, such as the popular SQL interface for relational database systems

Database System

The Purpose of database design is to create a database which:

- is a model of structures of reality

- supports queries and updates modeling processes of reality

- runs efficiently