Database Management Systems Notes
Subject Overview
Database Management Systems covers DBMS fundamentals and the three-level architecture, data models (ER, hierarchical, network, relational), the relational data model with normalization, and database protection and distributed databases. A 5-credit core theory paper.
Subject at a glance
4
Units
23
Topics
5
Credits
4
Infographics
Unit-wise Syllabus
4 units — open any unit for detailed topic-wise notes, diagrams and important exam questions
- File processing systems vs database systems
- database administrator responsibilities
- physical and logical data independence
- three-level architecture — external
- conceptual and internal levels
- External level
User views
- Conceptual level
Whole logical structure: tables, relationships
- Internal level
Physical storage on disk
Study guide
This unit compares file systems with database systems, covers the DBA's responsibilities, physical and logical data independence and the three-level architecture (external, conceptual, internal). Explain data independence with a simple example.
- Entity-Relationship model
- hierarchical model
- network model
- relational model
- comparison of network/hierarchical/relational models
Hierarchical
Tree of parent and child records
One-to-many only
Network
Graph of records and sets
Many-to-many
Relational
Tables of rows and columns
Through keys
ER model
Entities, attributes, relationships
Design tool for databases
Study guide
You study data models: Entity-Relationship, hierarchical, network and relational, with a comparison of the three record-based models. Draw an ER diagram for a college or library.
- Relational database
- relational algebra and calculus
- SQL
- dependencies — functional dependency
- multi-valued dependency
- join dependency
- normalization
- 1
Unnormalised data
Repeating groups
- 2
1NF
Atomic values, no repeating groups
- 3
2NF
No partial dependency on part of a key
- 4
3NF
No transitive dependency
- 5
BCNF
Every determinant is a candidate key
- 6
4NF and 5NF
No multi-valued or join dependencies
Study guide
You study the relational model: relational algebra and calculus, SQL, functional, multi-valued and join dependencies and normalisation. Practise normalising a table up to BCNF step by step.
- Recovery
- concurrency management
- database security
- integrity and control
- disaster management
- structure and design of distributed databases
Atomicity
All or nothing
Consistency
Valid state to valid state
Isolation
Transactions don't interfere
Durability
Committed changes survive failures
Study guide
You study database protection: recovery, concurrency control, security, integrity, disaster management and the structure and design of distributed databases. Understand why concurrency control is needed with a bank transfer example.
Why Database Management Systems Matters
Almost every application depends on a database, and SQL and database design are among the most requested skills for software and data jobs.
How to Prepare for Database Management Systems
- Practise SQL queries daily on a sample database.
- Learn to find candidate keys and normalise to 3NF and BCNF.
- Draw ER diagrams for several case studies.
Database Management Systems: Frequently Asked Questions
What is data independence?
Data independence is the ability to change the schema at one level without changing it at the next higher level.
What is normalisation?
Normalisation organises data into tables to reduce redundancy and avoid update anomalies.