Unit 1: Introduction to databases and data models
Database Management Systems-I notes · PTU syllabus (UGCC2512)
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Unit summary
Almost every application — banking, college ERPs, e-commerce, social media — stores its data in a database. A Database Management System (DBMS) is the software that stores, retrieves and protects that data. This unit introduces data, databases and DBMS, their applications, advantages and disadvantages, the people who use and manage databases, and the main data models.
After this unit you can
- Define data, information, database and DBMS
- Compare the file system approach with a DBMS
- Describe the roles of database users and the DBA
- Compare hierarchical, network, relational and object-oriented data models
PTU syllabus topics
- Definitions of data
- database and DBMS
- database applications
- advantages/disadvantages of DBMS
- roles of database users and administrators
- data model types (hierarchical, network, relational, object-oriented)
- External level
User views of the data
- Conceptual level
Logical structure of the whole database
- Internal level
How data is physically stored
Topic 1
Data, database and DBMS
- Data: raw facts (e.g. "Ana", 85, "BCA").
- Information: processed, meaningful data ("Ana scored 85 in BCA").
- Database: an organised collection of related data stored so it can be accessed easily.
- DBMS: software that creates, stores, manages and controls access to databases. Examples: MySQL, Oracle, PostgreSQL, SQL Server, MongoDB.
Applications: banking (accounts, transactions), airlines and railways (reservations), universities (students, results), hospitals, e-commerce (orders, inventory), telecom and social media.
Topic 2
File system vs DBMS
Redundancy
High: same data in many files
Controlled
Consistency
Inconsistent copies are common
Maintained by constraints
Data access
Need a new program for each query
Easy queries with SQL
Security
Weak
User-level access control
Concurrency
Problems with simultaneous users
Managed safely
Backup and recovery
Manual
Built in
Disadvantages of a DBMS: high cost of software and hardware, complexity, need for trained staff, and performance overhead for very small, simple applications.
Topic 3
Database users and the DBA
| User | Role |
|---|---|
| Database Administrator (DBA) | Manages the whole database: schema, security, backup, performance |
| Database designers | Decide the structure: tables, keys, relationships |
| Application programmers | Write programs that use the database |
| End users (naive and sophisticated) | Use the database through forms or queries |
Responsibilities of the DBA: defining the schema, granting access, backup and recovery, monitoring performance, and maintaining integrity and security.
Topic 4
Data models
A data model is a set of concepts for describing the structure of a database, its relationships and its constraints.
Hierarchical
Tree: one parent, many children
IBM IMS, file folders
Network
Graph: records linked by many-to-many sets
IDMS
Relational
Tables of rows and columns linked by keys
MySQL, Oracle
Object-oriented
Objects with data and methods
Multimedia, CAD databases
The relational model (E. F. Codd, 1970) is the most widely used because of its simplicity and the power of SQL.
Exam tip
Also mention the three-level architecture (external, conceptual, internal) and data independence if asked about DBMS architecture.
Key terms
- Database
- An organised collection of related data
- DBMS
- Software for creating and managing databases
- DBA
- The person responsible for managing the database
- Data redundancy
- Unnecessary duplication of data
- Data model
- Concepts for describing a database's structure
Quick revision
- Data → information; database → DBMS.
- DBMS reduces redundancy and inconsistency and adds security and concurrency.
- DBA manages schema, security, backup and performance.
- Models: hierarchical (tree), network (graph), relational (tables), object-oriented.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Differentiate between data and information.
- Q2.Define a DBMS and give two examples.
- Q3.List four advantages of a DBMS over a file system.
- Q4.What are the duties of a DBA?
- Q5.Name four data models.
Long-answer questions
- Q1.Compare the file processing system and the DBMS approach in detail.
- Q2.Explain the different types of database users and the role of the DBA.
- Q3.Explain the hierarchical, network and relational data models with diagrams.
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