Unit-1 :Introduction to Database : Database system applications.Characteristics and Purpose ofdatabase approach. People associated with a Database system. Data models. Databaseschema. Database architecture. Data independence . Database languages,E-R Model: Entity-Relationship modeling: E – R Model Concepts: Entity, Entity types,Entity sets, Attributes, Types of attributes.Relationships between the entities. Relationshiptypes, structural constraints. Weak entity types, E -R diagram - examples.

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Database Management Systems(DBMS):UNIT-I Introduction to Database(DBMS) BCA SEM-III

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  Database Management Systems(DBMS) Unit-I BCA Semester III1Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcaUnit-I: Introduction to DatabaseIntroduction to Database• A database is an organised collection of data that can be easily accessed, managed, andupdated.• Instead of storing information in separate files, a database keeps all data in a structuredform so that it can be used efficiently by different applications.• Databases are widely used in almost every field such as banking, education, business,hospitals, and government services.Database System ApplicationsDatabase systems are used in various real-life applications, such as:• Banking: Storing customer details, account information, and transaction records.• Airline and Railway Reservations: Managing booking details, schedules, andpassenger information.• Education: Student records, exam results, attendance management.• E-commerce: Product details, orders, payments, and customer information.• Hospitals: Patient records, doctor schedules, billing, and prescriptions.• Government: Aadhaar data, tax records, land records, etc.These applications use database systems because they allow fast, secure, and accuratehandling of large amounts of data.Characteristics of the Database Approach1. Data is stored in a central placeAll related data is stored together instead of scattered across multiple files.2. Reduced data redundancyDuplicate data is minimised because the same information is not stored repeatedly.3. Better data sharingMultiple users and applications can access the same data at the same time.4. Improved data securityAccess permissions can be given to authorised users only.5. Data consistency and integritySince data is centralised, it remains accurate and consistent across the system.
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  Database Management Systems(DBMS) Unit-I BCA Semester III2Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca6. Easy data accessUsing database languages such as SQL, data can be retrieved and updated easily.Purpose of the Database Approach• To manage large volumes of data efficientlyDatabases help in storing huge amounts of data in an organised manner.• To allow safe multi-user accessMany users can work on the same data without affecting each other.• To ensure data securitySensitive data can be protected using authentication and permissions.• To maintain accuracy and consistencyThe database system automatically checks rules so that incorrect data is not stored.• To reduce duplication and save storageSince data is not repeated unnecessarily, storage is used more effectively.• To support easy data retrieval and reportingComplex queries and reports can be generated quickly.People Associated with a Database SystemA database system is used and managed by different types of people. Each group has specificroles and responsibilities to ensure that the database works smoothly, securely, and efficiently.The main people associated with a database system are:
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  Database Management Systems(DBMS) Unit-I BCA Semester III3Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca1. Database Administrator (DBA)• The DBA is responsible for the overall management of the database system.• Duties include installing the DBMS, creating databases, setting user permissions,ensuring security, taking backups, and monitoring performance.• They make sure that the database runs without errors and remains available to users.2. Database Designers• These people design the structure of the database before it is created.• They identify what data needs to be stored, how the data should be organised, andwhat relationships should exist between different data items.• They decide the tables, attributes, keys, and constraints.3. Application Programmers / Developers• They write programs and applications that interact with the database.• They use languages like Java, Python, PHP, or SQL to create forms, screens, reports,and interfaces used by end users.• Their programs help users add, update, delete, or retrieve data.4. End UsersEnd users are the people who actually use the database through applications. They are ofdifferent types:a) Casual Users• Use the database occasionally.• Write simple queries to access information.• Example: A manager checking monthly sales.b) Naïve Users / Parametric Users• Use pre-defined forms or commands.• Do not know how the database works internally.• Example: A bank clerk entering deposits or withdrawals in a system.c) Sophisticated Users• Write complex queries and use advanced tools to analyse the database.• Example: Data scientists, analysts.d) Stand-alone Users
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  Database Management Systems(DBMS) Unit-I BCA Semester III4Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca• Use ready-made applications (like MS Access) to manage their own personal data.5. System Analysts• Study the requirements of an organisation and decide what kind of databaseapplications are needed.• They communicate between end users and developers.6. Database System Developers• They design and develop the DBMS software itself like Oracle, MySQL, SQL Server,etc.• Their role is more technical and requires deep knowledge of database theory andsystem programming.Data Models, Database Schema, Database Architecture, Data Independence,Database Languages1. Data ModelsA data model is a way to describe how data is organised, stored, and related inside adatabase.It provides a framework to understand the structure of the data.Types of Data Modelsa) Hierarchical Model• Data is arranged in a tree-like structure (parent–child).• Easy to understand but not flexible.b) Network Model• Data is represented as a graph (many-to-many relationships).• More flexible than hierarchical.
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  Database Management Systems(DBMS) Unit-I BCA Semester III5Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcac) Relational Model• Data is stored in tables (rows and columns).• Most widely used model (e.g., MySQL, Oracle, SQL Server).d) Object-Oriented Model• Data is stored as objects (similar to real-world entities).• Used in advanced applications.
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  Database Management Systems(DBMS) Unit-I BCA Semester III6Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcae) Entity-Relationship (ER) Model• Uses entities, attributes, and relationships.• Mostly used during database design.2. Database SchemaA database schema is the complete logical structure of the database.It describes how the data is organised and how different tables are related.• It includes tables, fields, data types, relationships, and constraints.• Schema acts like a blueprint or plan of the database.Types of Schemas• Physical Schema: How data is actually stored on the storage devices.• Logical Schema: Structure of data at a logical level (tables, relationships).• External Schema: Different user views of the same database.
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  Database Management Systems(DBMS) Unit-I BCA Semester III7Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca3. Database ArchitectureDatabase architecture describes the structure or framework that shows how the databasesystem works.The most common architecture is the Three-Level Architecturea) External Level (View Level)• Shows how individual users see the data.• Each user gets a customised view.b) Conceptual Level (Logical Level)• Shows the complete logical structure of the database.• Contains all entities, relationships, and constraints.c) Internal Level (Physical Level)• Shows how the data is physically stored (files, indexes, storage paths).
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  Database Management Systems(DBMS) Unit-I BCA Semester III8Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca4. Data IndependenceData independence means that changes in one level of the database architecture do not affectother levels. This makes the system flexible and easy to maintain.Types of Data Independencea) Logical Data Independence• Ability to change the logical schema (like adding a new table) without affecting userviews.b) Physical Data Independence• Ability to change the physical storage (like changing file structure) without affectingthe logical schema.5. Database LanguagesDatabase languages are used to define, manipulate, and control data in a DBMS.
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  Database Management Systems(DBMS) Unit-I BCA Semester III9Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcaa) DDL – Data Definition LanguageUsed to define the structure of the database.Commands: CREATE, ALTER, DROP, TRUNCATEb) DML – Data Manipulation LanguageUsed to access and modify data.Commands: INSERT, UPDATE, DELETE, SELECTc) DCL – Data Control LanguageUsed to control access and permissions.Commands: GRANT, REVOKEd) TCL – Transaction Control LanguageUsed to manage database transactions.Commands: COMMIT, ROLLBACK, SAVEPOINTE–R Model (Entity–Relationship Model)• The Entity–Relationship (E–R) Model is a high-level data modelling technique usedto design the logical structure of a database.• It helps us understand how data is organised and how different data items are relatedbefore the actual database is created.• The E–R model is represented using E–R diagrams, which contain entities, attributes,and relationships.
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  Database Management Systems(DBMS) Unit-I BCA Semester III10Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcaE–R Model Concepts1. EntityAn entity is any real-world object or thing about which we want to store information in thedatabase.Examples:• Student, Teacher, Course, Employee, Department, Product, Hospital, Patient.Entities are usually nouns.2. Entity TypesAn entity type is a collection or category of entities that have the same properties.Example:• The entity Student is an entity type.• All individual students (Rahul, Priya, Akash) are entities belonging to this entity type.An entity type defines a set of attributes that describe its characteristics.3. Entity SetAn entity set is a group of similar entities that belong to the same entity type.Example:• All students in a college form a Student entity set.• All employees in a company form an Employee entity set.Entity sets are usually represented by rectangles in E–R diagrams.4. AttributesAttributes are the properties or characteristics that describe an entity.Example (for a Student entity):• Student_ID• Name• Age• Address
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  Database Management Systems(DBMS) Unit-I BCA Semester III11Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca• Phone_Number• DepartmentTypes of Attributesa) Simple AttributeCannot be divided into smaller parts.Example: Age, Salary.b) Composite AttributeCan be divided into sub-parts.Example: Address → House No, Street, City, PIN.c) Single-Valued AttributeHas only one value for a given entity.Example: Aadhaar Number, Roll Number.d) Multi-Valued AttributeCan have more than one value.Example: Phone Numbers, Email IDs.e) Key AttributeUniquely identifies an entity in an entity set.Example: Employee_ID, Student_ID.f) Derived AttributeValue can be derived from another attribute.Example: Age can be derived from Date_of_Birth.Relationships Between EntitiesA relationship is an association between two or more entities.Example:• A Student enrolls in a Course.• An Employee works in a Department.Relationships are represented using diamonds in ER diagrams.
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  Database Management Systems(DBMS) Unit-I BCA Semester III12Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcaRelationship Types (Degree of Relationship)a) Unary Relationship (1-entity)Relationship among entities of the same type.Example: An Employee manages another Employee.b) Binary Relationship (2-entities) — most commonExample: Student enrolls in Course.c) Ternary Relationship (3-entities)Example: Doctor treats Patient using Medicine.Structural ConstraintsStructural constraints define how many entities can participate in a relationship.They include cardinality and participation.
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  Database Management Systems(DBMS) Unit-I BCA Semester III13Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcaa) Cardinality RatioSpecifies the number of entities that can be associated.1. One-to-One (1:1)Example:• A person has one passport.• One passport belongs to one person.2. One-to-Many (1:N)Example:• One department has many employees.• Each employee belongs to one department.3. Many-to-One (N:1)Example:• Many students belong to one class.4. Many-to-Many (M:N)Example:• Students enroll in many courses.• Each course has many students.Participation Constraints
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  Database Management Systems(DBMS) Unit-I BCA Semester III14Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bca1. Total ParticipationEvery entity must participate in the relationship.Example:• Every Employee must belong to a Department.Represented by double line.2. Partial ParticipationSome entities may or may not participate.Example:• Not every employee manages a project.Represented by single line.Weak Entity TypesA weak entity:• Cannot be uniquely identified by its own attributes.• Depends on another entity (called owner or strong entity).• Identified by a partial key.• Represented using double rectangle.
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  Database Management Systems(DBMS) Unit-I BCA Semester III15Notes by Dr. Chandrakantha T S, Vagdevi College of BCA, Melinakuruvalli, Thirthahalli-577 432For more notes and resources, visit: https://sites.google.com/view/chandrakanthats/bcaExample:• Dependent depends on Employee.Dependent entity may have:• Partial key: Dependent_Name• Attributes: Age, RelationshipWeak entity must have total participation with the owner entity.E–R Diagram – ExamplesExample 1: Student–Course ER Diagram (M:N relationship)Example 2: Employee–Department (1:N relationship)*** ** ***