Database management system full theory portion is covered. It's helpful to students who are in any management courses.all the best to all of you, this ppt might be helpful for you.Database management system full theory portion is covered. It's helpful to students who are in any management courses.all the best to all of you, this ppt might be helpful for you.Database management system full theory portion is covered. It's helpful to students who are in any management courses.all the best to all of you, this ppt might be helpful for you.Database management system full theory portion is covered. It's helpful to students who are in any management courses.all the best to all of you, this ppt might be helpful for you.

1. Introduction
Database Management Systems

2. What is a database?
 A very large, integrated collection of
data.
 Models real-world application :
– Entities (students, courses)
– Relationships (links,refrences)
 Usually data is too large to fit into main
memory, and often used by many users

3. Database applications ?
 E-commerce : Amazon.com, etc.
 Airlines and travel services
 Scientific data such as biology,
oceanography, etc.
 Spatial data such as maps, travel
networks,
 World Wide Web
 Digital libraries of artifacts of any kind

4. What is a DBMS ?
 DBMS stands for Database
Management System
 software package designed to store,
manage and provide access to
databases.

5. Why Study Databases??
 Shift from computation to information
 Datasets increasing in diversity and volume.
– Digital libraries, interactive video, Human Genome
project, EOS project
– ... need for DBMS exploding
 DBMS encompasses most of CS :
– OS, languages, theory, AI, multimedia, logic
?

6. Terminology : Data Models
 A data model :
– is a collection of concepts for describing data.
 A schema :
– is a description of a particular collection of data,
using the given data model.
 The relational model of data
– The most widely used model today.
– Main concept: relation, basically a table with rows
and columns.
– Every relation has a schema, which describes the
columns, or fields.

7. Data Definition Language (DDL)
 Specification notation for defining the
database schema
 DDL compiler generates a set of tables
stored in a data dictionary
 Data dictionary contains metadata (data
about data)
 Data storage and definition language –
special type of DDL in which the storage
structure and access methods used by the
database system are specified

8. Data Manipulation Language (DML)
 Language for accessing and
manipulating the data organized by the
appropriate data model
 Two classes of languages
– Procedural – user specifies what data is
required and how to get those data
– Nonprocedural – user specifies what data
is required without specifying how to get
those data

9. Database schema
 Its structure described in a formal
language supported by (DBMS) and
refers to the organization of data to
create a blueprint of how a database will
be constructed

10. DBMS Keys
 A key is an attribute also known as a
combination of attribute that is used to
identify records. Sometimes we might
have to retrieve data from more than
one table, in those cases we require to
join tables with the help of keys. The
purpose of the key is to bind data
together across tables without repeating
all of the data in every table.

11. Levels of Abstraction
 Many views:
– Views describe how users
see the data.
 Single conceptual (logical)
schema
– Conceptual schema defines
logical structure
 Single physical schema:
– Physical schema describes
the files and indexes used.
* Schemas are defined using Data Definition Language ;
* data is modified/queried using Data Manipulation Language
Physical Schema
Conceptual Schema
View 1 View 2 View 3

12. Example: University Database
 Conceptual schema:
– Students(sid: string, name: string, login: string,
age: integer, gpa:real)
– Courses(cid: string, cname:string, credits:integer)
– Enrolled(sid:string, cid:string, grade:string)
 Physical schema:
– Relations stored as unordered files.
– Index on first column of Students.
 External Schema (View):
– Course_info(cid:string, enrollment:integer)
– CS542Students(sid: string, grade:string)

13. Data Independence
 Applications insulated from how data is
structured and stored.
 Logical data independence:
– Protection from changes in logical structure
of data.
 Physical data independence:
– Protection from changes in physical
structure of data.
* One of the most important benefits of using a DBMS!

14. Files vs. DBMS
 Stage large datasets between main memory
and secondary storage (buffering, page-
oriented access)
 Must write special code for different queries
 Must protect data from inconsistency due to
multiple concurrent users
 Must manage crash recovery in some
special-purpose manner
 Must provide good methods for access
control
If we were to use files, we would have to :

15. Why Use a DBMS?
 Reduced application development time.
 Data independence
 Efficient data access.
 Data integrity under updates.
 Concurrent access
 Recovery from crashes.
 Security
 Uniform data administration.

16. Transaction Management
 A transaction is a collection of operations that
performs a single logical function in a
database application.
 Transaction-management component
ensures that the database remains in a
consistent (correct) state despite system
failures (e.g. power failures and operating
system crashes) and transaction failures.
 Concurrency-control manager controls the
interaction among the concurrent
transactions, to ensure the consistency of the
database.

17. Concurrency Control
 Concurrent execution of user programs
is essential for good DBMS performance.
– Because disk accesses are frequent, and relatively
slow, it is important to keep CPU humming by
working on several user programs concurrently.
 Interleaving actions of different user programs
can lead to inconsistency:
– e.g., check is cleared while account balance is being
computed.
 DBMS ensures such data inconsistency
problems don’t arise:
– E.g., users can pretend they are using a single-user
system

18. Concurrency Control

19. Key Concepts of CC
 Key concept is transaction, which is an
atomic sequence of multiple database
actions (reads/writes)
 Each transaction, executed completely,
must leave the DB in a consistent state
 Utilize locking of resources and other
protocols for guaranteeing consistency.

20. System Crash : Ensuring Atomicity
 If system crashes in the middle of a
process, then DBMS ensures atomicity
 Idea: Keep a log (history) of all actions
carried out by the DBMS while
executing a process :
– Before a change is made to database,
corresponding log entry is forced to a safe
location (commit of transaction)
– After a crash, the effects of partially
executed transactions are undone using
the log (rollback of transaction)

21. Storage Management
 A storage manager is a program module that
provides the interface between the low-level
data stored in the database and the
application programs and queries submitted
to the system.
 The storage manager is responsible for the
following tasks:
– Interaction with the file manager
– Efficient storing, retrieving, and updating of data

22. Databases make these folks
happy ...
 End users and DBMS vendors
 DB application programmers
– E.g., smart webmasters
 Database administrator (DBA)
– Designs logical /physical schemas
– Handles security and authorization
– Data availability, crash recovery
– Database tuning as needs evolve
Must understand how a DBMS works!

23. Structure of a DBMS
 A typical DBMS
has a layered
architecture.
 Concurrency
control and
recovery
components not
shown.
Query Optimization
and Execution
Relational Operators
Files and Access Methods
Buffer Management
Disk Space Management
DB
These layers
must consider
concurrency
control and
recovery

24. KEYS
 Associative addressing is based on keys – a
column, or group of columns, used to identify
rows.
 Simple key – a key formed from a single column
 Composite key – a key formed from several
columns
 The relational model has five kinds of keys
• Super
• Candidate
• Primary
• Alternate (secondary)
• Foreign

25. Super Key
 A superkey is any set of attributes that
uniquely identifies a row. A superkey
differs from a candidate key in that it
does not require the non redundancy
property.

26. Candidate
 A candidate key is an attribute (or set of
attributes) that uniquely identifies a row. A
candidate key must possess the following
properties:
Unique identification - For every row the
value of the key must uniquely identify that
row.
Non redundancy - No attribute in the key can
be discarded without destroying the property
of unique identification.

27. Primary Key
 A primary key is the candidate key
which is selected as the principal unique
identifier. Every relation must contain a
primary key. The primary key is usually
the key selected to identify a row when
the database is physically implemented.
For example, a part number is selected
instead of a part description

28. Alternate (secondary)
 The Candidate key which is not
selected for primary key are known as
secondary or alternate key

29. Forign Key
 A foreign key is an attribute (or set of
attributes) that appears (usually) as a
non key attribute in one relation and as
a primary key attribute in another
relation. I say usually because it is
possible for a foreign key to also be the
whole or part of a primary key

30. CIS-552 Introduction 31
Overall System Structure
indices Statistical data
Data files Data dictionary
disk storage

31. Summary
 DBMS used to maintain & query large datasets.
 Benefits include recovery from system crashes,
concurrent access, quick application
development, data integrity and security.
 Levels of abstraction give data independence.
 A DBMS typically has a layered architecture.
 DBAs hold rewarding jobs. 
 DBMS R&D is one of the broadest,
most exciting areas in CS.