- DBMS - Home
- DBMS - Overview
- DBMS - Architecture
- DBMS - Data Models
- DBMS - Data Schemas
- DBMS - Data Independence
- DBMS - System Environment
- Centralized and Client/Server Architecture
- DBMS - Classification
- Relational Model
- DBMS - Codd's Rules
- DBMS - Relational Data Model
- DBMS - Relational Model Constraints
- DBMS - Relational Database Schemas
- DBMS - Handling Constraint Violations
- Entity Relationship Model
- DBMS - ER Model Basic Concepts
- DBMS - ER Diagram Representation
- Relationship Types and Relationship Sets
- DBMS - Weak Entity Types
- DBMS - Generalization, Aggregation
- DBMS - Drawing an ER Diagram
- DBMS - Enhanced ER Model
- Subclass, Superclass and Inheritance in EER
- Specialization and Generalization in Extended ER Model
- Data Abstraction and Knowledge Representation
- Relational Algebra
- DBMS - Relational Algebra
- Unary Relational Operation
- Set Theory Operations
- DBMS - Database Joins
- DBMS - Division Operation
- DBMS - ER to Relational Model
- Examples of Query in Relational Algebra
- Relational Calculus
- Tuple Relational Calculus
- Domain Relational Calculus
- Relational Database Design
- DBMS - Functional Dependency
- DBMS - Inference Rules
- DBMS - Minimal Cover
- Equivalence of Functional Dependency
- Finding Attribute Closure and Candidate Keys
- Relational Database Design
- DBMS - Keys
- Super keys and candidate keys
- DBMS - Foreign Key
- Finding Candidate Keys
- Normalization in Database Designing
- Database Normalization
- First Normal Form
- Second Normal Form
- Third Normal Form
- Boyce Codd Normal Form
- Difference Between 4NF and 5NF
- Structured Query Language
- Types of Languages in SQL
- Querying in SQL
- CRUD Operations in SQL
- Aggregation Function in SQL
- Join and Subquery in SQL
- Views in SQL
- Trigger and Schema Modification
- Storage and File Structure
- DBMS - Storage System
- DBMS - File Structure
- DBMS - Secondary Storage Devices
- DBMS - Buffer and Disk Blocks
- DBMS - Placing File Records on Disk
- DBMS - Ordered and Unordered Records
- Indexing and Hashing
- DBMS - Indexing
- DBMS - Single-Level Ordered Indexing
- DBMS - Multi-level Indexing
- Dynamic B- Tree and B+ Tree
- DBMS - Hashing
- Transaction and Concurrency
- DBMS - Transaction
- DBMS - Concurrency Control
- DBMS - Deadlock
- Backup and Recovery
- DBMS - Data Backup
- DBMS - Data Recovery
- DBMS Useful Resources
- DBMS - Quick Guide
- DBMS - Useful Resources
- DBMS - Discussion
DBMS - Data Models
Data models define how the logical structure of a database is modeled. Data Models are fundamental entities to introduce abstraction in a DBMS. Data models define how data is connected to each other and how they are processed and stored inside the system.
The very first data model could be flat data-models, where all the data used are to be kept in the same plane. Earlier data models were not so scientific, hence they were prone to introduce lots of duplication and update anomalies.
Entity-Relationship Model
Entity-Relationship (ER) Model is based on the notion of real-world entities and relationships among them. While formulating real-world scenario into the database model, the ER Model creates entity set, relationship set, general attributes and constraints.
ER Model is best used for the conceptual design of a database.
ER Model is based on −
Entities and their attributes.
Relationships among entities.
These concepts are explained below.
Entity − An entity in an ER Model is a real-world entity having properties called attributes. Every attribute is defined by its set of values called domain. For example, in a school database, a student is considered as an entity. Student has various attributes like name, age, class, etc.
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Relationship − The logical association among entities is called relationship. Relationships are mapped with entities in various ways. Mapping cardinalities define the number of association between two entities.
Mapping cardinalities −
- one to one
- one to many
- many to one
- many to many
Relational Model
The most popular data model in DBMS is the Relational Model. It is more scientific a model than others. This model is based on first-order predicate logic and defines a table as an n-ary relation.
The main highlights of this model are −
- Data is stored in tables called relations.
- Relations can be normalized.
- In normalized relations, values saved are atomic values.
- Each row in a relation contains a unique value.
- Each column in a relation contains values from a same domain.