Introduction to Databases and DBMS

• A database is a structured set of data, modeling a real world, recorded on computer media and satisfying several users simultaneously
• Data consists of facts and knowledge recorded with implicit meaning
• Real world is an organization which includes companies, hospitals and universities
• The objective is to have a computer system that allows recording sales and checking item availability

Why Databases?

• A company specializing in household appliances may want to acquire a computer system to manage sales and employee work
• The types of information to be treated include item availability (e.g., "Tel888" Toshiba Television), sales records (e.g., seller "Sami" sold two "Bosch" washing machines), and stock quantities (e.g., item "Ref567" Samsung Refrigerator quantity is 4)

Database Management System (DBMS)

• A DBMS is a software that supports structuring, storing, and maintaining a database
• The DBMS serves as the primary interface between computer scientists, data (schemas, programming of applications), users and data for consultations and updating
• Examples of DBMS software include Oracle, Microsoft SQL Server, MySQL, PostgreSQL, SQLite, Firebird, Sybase, and Access

Database System

• The database system consists of the DBMS and the data itself, sometimes including applications
• A metabase comprises metadata that describes the database.

Possible Treatments for Databases

• Can list top selling items, sale amount for each salesman and increase the price of all items from the manufacturer Samsung by 5%

Database Needs

• Databases store large volumes of information with predefined structures and standard treatments and allow sharing of information between multiple users and ensures consistency.

Data Model

• A data model describes a database using concepts offered by a DBMS, including data, links between data, and data semantics, enabling data manipulation
• In 1965 the Hierarchical Model was implemented by IBM and North American Rockwell
• In 1964-65 the Network Model was implemented by Honeywell
• In 1970 the Relational Model was proposed by E.F. Codd (IBM), with the first system marketed in 1982
• In 1990 the Object-Oriented Model proposed models of OOP languages such as C++ and Smalltalk
• Currently the most popular model is the Relational-Object Model
• Not a model but NoSQL families developed in parallel and meet different needs (2009)

DBMS Features

• Defines a DB in terms of data types, structures & constraints
• Allows querying of the database
• Allows updating data like insertion Modification & Deletion
• Definition of integrity constraints and database updates must respect integrity constraints
• Database shared by several users, and certain data should only be accessible to authorized persons
• defines which information should be protected from which people
• Simultaneous access to data by multiple users
• Detect Possible conflicts
• Treat Conflicts
• Ensures system restart in the case of a software or hardware incident and puts the DB in a consistent state

DBMS Languages

• Database languages are specialized languages used to interact with databases, enabling tasks like defining, controlling, and manipulating data
• There are four main types of DBMS languages: DDL, DCL, DML, TCL
• DDL (Data Definition Language), which is used to create and modify the structure of database objects
• DCL (Data Control Language), which controls access permissions and helps grant or revoke privileges
• DML (Data Manipulation Language), which manages and manipulates data within a database, performing operations like inserting, updating, selecting, and deleting
• TCL (Transaction Control Language), which manages and controls transactions in a database, grouping them into logical units to ensure data integrity and consistency during complex operations