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Database Systems Data A collection of raw facts and figures is called data Data is given to the computer for processing Data is collected from different sources for different purposes Data is a vital source for any organization Data is considered as a resource because it provides correct information for making proper and timely decisions Types of Data Numeric Data Alphabetic Data Alphanumeric Data Image Data Audio Data Video Data Information The processed data is called information Information is organized and processed form of data More meaningful than data Used for making decisions Metadata Metadata can be defined as data about data It is used to describe the properties and characteristics of some other data Metadata describes the size, format and other characteristics of data It includes the rules and constraints about the data It is very important to ensure the integrity of the data Example ◦ When creating table, specify the data type, size, format and other constraints Database Database is organized collection of related data ◦ The word organized means data is stored in such a way that the user can store, manipulate and retrieve data easily ◦ The word related means that the database is normally created to store the data about the particular topic ◦ For example, database for students, employees Tables Table is the fundamental object of database structure Store data Consists of rows and columns S.No Name Qualification Email 1 Usman B.Sc. [email protected] 2 Abdullah M.Sc. [email protected] 3 Ejaz M.Sc [email protected] Examples of Databases Phone directory Library Accounts College Components of Database System Data Hardware ◦ ◦ ◦ ◦ Main Memory Processor I/O Devices Secondary Storage Software ◦ Operating System Software ◦ DBMS Software ◦ Application Program and Utilities Personnel ◦ Database Administrator ◦ Application Programmers ◦ End Users Hierarchy of Data Data in computer is classified in a hierarchy A Database contains files A file contains records A record contains fields A field consists of characters A byte is used to represent the characters like ‘T’ Relationships A relationship is a logical connection between tables A relationship is established on the basis of interaction among these tables The relationship is established by connection one or more fields of two tables The fields used to connect two tables normally have same name, data type and size Types of Relationship One-to-One Relationship One-to-Many Relationship Many-to-Many Relationship Keys A key is an attribute or set of attributes that uniquely identifies a tuple in a relation The keys are defined in table to access or sequence the stored data quickly and smoothly They are also used to create relationship between different tables Types of Keys Primary Key Candidate Key Alternate Key Composite Key Foreign Key Secondary Key Sort/Control Key Referential Integrity Referential integrity is a constraint on foreign key value It states that if a foreign key exists in a relation, the foreign key value must match the primary key value of some tuple’s in its parents relation Referential integrity preserves the defined relationship between tables when records are added or deleted Ensures the key values are consistent across the tables Maintaining Data A set of procedures used o keep data current is called file maintenance or data maintenance ◦ ◦ ◦ ◦ Adding Records Changing Records Deleting Records Data Validation Alphabetic/Numeric Check Range Check Consistency Check Completeness Check Database Security Database security is a process of protecting database from intentional or accidental threats It includes the security of hardware, software, people and data related to a database Basic purpose is to minimize the losses that may occur due to different security threats Factors Related to Database Security Theft and Fraud Loss of Confidentiality Loss of Privacy Loss of Integrity Loss of Availability Database Security Threats A database security threat is a situation or event that may affect a system adversely Threats may occur intentionally or unintentionally A threat may be a result of an event that involves a person or action to harm the system It may result in tangible and intangible damage An organization must identify all possible threat that may damage it Measures against Threats Authorization Authentication Views Backup and Recovery Integrity Encryption Backup and Recovery A database can be damaged or destroyed due to several reasons such as: Hardware Failure Software Problem Human Error Fire or flood References Introduction to Information Technology by Riaz Shahid, CM Aslam and Safia Iftikhar The Concepts of Information Technology by Imran Saeed, Ahsan Raza, Tariq Mehmood and Zafar Hussain
