DBMS Concepts - Database Management System Video Lecture - Class 12

hello students welcome to the lecture on
database management system concepts and
after this lecture we will be able to
learn the following objectives
understand the concepts of database
management system discuss about the
entity relationship model explain the
three schema architecture define the
DBMS languages and list all the
advantages and disadvantages of using
DBMS let's start with database concepts
data is in contrast to information in
raw or unorganized forms such as
alphabets numbers or symbols that refers
to or represents conditions ideas or
objects the term database we usually
mean a group of data that is stored on
the basis of a system which data do not
necessarily get stored on a computer
types of information handling a database
is a collection of the different
phenomena that we are interested in an
organized unit now let me tell you what
are the types of information handling we
can store our data in different stocks
and establish a connection between them
with the help of a program we can store
our data in text mode also this is a
formulation of knowledge in a text like
way instead of a data like form we call
the tool itself a text manager and the
text managing system is a database
database administration database is a
collection of data which stores the data
required for a given task in an
organized way grants access to them and
at the same time safeguards the
integrity of the units and protects them
from any harm steps to perform mode
based database
are we create the entities along with
their properties we establish the
relationship between them the rest is
dealt with by the database handler
entity we call the thing that something
that we want to describe with the help
of our knowledge and entity the specific
entities are known as entity occurrences
as you can see in the figure here is the
example of entity property we call the
thing that something that we used to
describe the phenomena which we are
interested in a property the concrete
value of a property is the property
value the property value set is the term
used for all the values present in a
specific time both entity and property
are relative terms you can differentiate
both as primarykey the property of an
entity which takes up a different value
for every entity occurrence is known as
the atom or identifier of the entity it
is also known as primary key we call the
relation between the entities a
relationship components of database
systems data is a very important
component of the database system data
acts as a bridge between the machine
parts that is hardware and software and
the users which directly access it or
access it through some application
programs data may be of different types
user data it consists of a table tables
of data called relation relations where
columns are called fields of attributes
and rows are called records for tables a
relation must be structured properly
metadata a description of the structure
of the database is known as metadata
it basically means data about data
system tables store the metadata which
includes number of tables
table names number of fields and field
names primary key fields application
metadata it stores the structure and
format of queries reports and other
applications companies hardware the
hardware consists of the secondary
storage devices such as magnetic disks
hard-disk zip disks floppy disks optical
disks cd-rom magnetic tapes etc on which
data is stored together with the
input/output devices mouse keyboard
printers processors main memory etc
which are used for storing and
retrieving the data in a fast and
efficient manner software the software
part consists of DBMS which acts as a
bridge between the user and the database
or in other words software that
interacts with the users application
programs and database and file system of
a particular storage media hard disk
magnetic tapes etc to insert update
delete and retrieve data database engine
the database engine is the core service
for storing processing and securing data
the database engine provides controlled
access and rapid transaction processing
to meet the requirements of the most
demanding data consuming applications
within your enterprise example Microsoft
SQL Server database user here are four
different types of database users
application programmers a person who
prepares application programs are called
application programmer sophisticated
users sophisticated users interact with
the system without writing programs
instead they form their requests in a
database query language specialized
users some sophisticated users write
specialized database application that
does not fit into
traditional data processing framework
end-users unsophisticated users interact
with the system by invoking one of the
permanent application programs that have
been written previously thus they are
persons who use the information
generated by a computer-based system
database management system basically it
is a set of computer programs that
controls maintenance and the use of a
database the database management systems
are used for recording storage and
management of the data in a database the
systems designed to make easier the
management of the databases is called
database management systems we are
familiar with Microsoft Access which is
also a database management system we can
use it to make new databases or add
delete modify or search for data in the
already existing databases here you can
see there are some main functions of the
database management systems which are
you can make new databases also you can
define the contents of the databases
make sure the data has been stored
properly you can query the required data
you can also protect the data as well
moreover you can secure the data you
have all the rights to access the data
but carefully easy to access you can
organize the physical data structures
advantages and disadvantages of database
in this section we will discuss about
some advantages and disadvantages of
database some of the advantages are
controlling redundancy means repetition
every user group maintains its own files
for handling its data processing
applications redundancy in storing the
same data multiple times leads to
several problems by this technique
it controls the duplicate values
performs on the applications restricting
unauthorized access when multiple users
share a large database it is likely that
most users will not be authorized to
access all information in the database
databases can be used to provide
resistant storage for program objects
and data structures this is one of the
main reasons for object-oriented
database systems database systems must
provide capabilities for efficiently
executing queries and updates because
the database is typically stored on the
disk the DBMS must provide specialized
data structures and search techniques to
speed up disk search for the desired
records a DBMS must provide facilities
for recovering from hardware or software
failures the backup and recovery
subsystem of the DBMS is responsible for
recovery because many types of users
with varying levels of technical
knowledge use a database a DBMS should
provide a variety of user interfaces
these include query languages for casual
users programming language interfaces
for application programmers forms and
command codes for parametric users and
menu driven interfaces and natural
language interfaces for stand-alone
users a database may include numerous
varieties of data that are interrelated
in many ways a DBMS must have the
capability to represent a variety of
complex relationships among the data to
define new relationships as they arise
and to retrieve an update related data
easily and efficiently most database
applications have certain integrity
constraints that must hold for the data
a DBMS should provide capabilities for
defining and enforcing these khans
trains some database systems provide
capabilities for defining deduction
rules for inferencing new information
from the stored data base facts such
systems are called deductive database
systems potential for enforcing
standards the database approach permits
the DBA to define and enforce standards
among database users in a large
organization this facilitates
communication and cooperation among
various departments projects and users
within the organization standards can be
defined for names and formats of data
elements display formats report
structures terminology and so on
disadvantages when information is
centralized and is made available to
users from remote locations the
possibilities of abuse are often more
than in a conventional data processing
system since the database is accessible
to users remotely adequate controls are
needed to control users updating data
and to control data quality with
increased number of users accessing data
directly there are enormous
opportunities for users to damage the
data the main threat to data integrity
comes from several different users
attempting to update the same data at
the same time centralizing all data of
an enterprise in one database may mean
that the database becomes an
indispensable resource database models a
data model is a collection of concepts
and rules for the description of the
structure of the database structure of
the database means the data types the
constraints and the relationships for
the description or storage of data the
network model and the hierarchical model
are the predecessors of the relational
model they build upon individual data
and are able to express hierarchical or
network like structures of the real
world the relational model is in today's
DBMS most often implemented database
model it defines the database as a
collection of tables relations which
contain all data object oriented models
define a database as a collection of
objects with features and methods object
oriented models are very powerful but
also quite complex with the relatively
new object relational database model is
the widespread and simple relational
database model extended by some basic
object-oriented concepts the three
schema architecture the three schema
architecture is a convenient tool with
which the user can visualize the schema
levels in a database system the three
level a and si architecture has an
important place in database technology
development because it clearly separates
the users external level the databases
conceptual level and the internal
storage level for designing a database
it is very much applicable in the design
of dbmss even today let us study the
three levels of DBMS the internal level
has an internal schema which describes
the physical storage structure of the
database the internal schema uses a
physical data model and describes the
complete details of data storage and
access paths for the database the
conceptual level has a conceptual schema
which describes the structure of the
whole database for a community of users
the external of view label includes a
number of external schemas or user views
each external schema describes the part
of the database that a particular user
group is interested in and hides the
rest of the database from that user
dbms languages once the design of a
database is completed and a DBMS is
chosen to implement the database the
first step is to specify conceptual and
internal schemas for the database and
any mappings between the two data
definition language DDL in many DBMS is
where no strict separation of levels is
maintained one language called the data
definition language DDL is used by the
DBA and by database designers to define
both schemas the DBMS will have a DDL
compiler whose function is to process
DDL statements in order to identify
descriptions of the schema constructs
and to store the schema description in
the DBMS catalog for truth 3 schema
architecture we would need a third
language the view definition language
vdl to specify user views and their
mappings to the conceptual schema but in
most DBMS --is the DDL is used to define
both conceptual and external schemas
data manipulation language DML once the
database schemas are compiled and the
database is populated with data users
must have some means to manipulate the
database typical manipulations include
retrieval insertion deletion and
modification of the data the DBMS
provides a set of operations or a
language called the data manipulation
language DML for these purposes let us
study the main types of DMLs
high-level a high-level or non
procedural DML can be used on its own to
specify complex database operations
concisely many DBMS a--'s allow high
level DML stay
one's either to be entered interactively
from a display monitor or terminal or to
be embedded in a general-purpose
programming language low-level language
a low-level or procedural DML must be
embedded in a general-purpose
programming language
this type of DML typically retrieves
individual records or objects from the
database and processes each separately
storage management the collection of
data that makes up a computerized
database must be stored physically on
some computer storage medium the DBMS
software can then retrieve update and
process this data as needed computer
storage media form a storage hierarchy
that includes two main categories
primary storage this category includes
storage media that can be operated on
directly by the computers central
processing unit CPU such as the
computer's main memory and smaller but
faster cache memories primary storage
usually provides fast access to data but
is of limited storage capacity secondary
and tertiary storage this category
includes magnetic disks optical disks
cd-roms DVDs and other similar storage
media and tapes hard disk drives are
classified as secondary storage
whereas removable media such as optical
disks and tapes are considered tertiary
storage transaction a transaction is an
executing program that includes some
database operations such as reading from
the database or applying insertions
deletions or updates to the database at
the end of the transaction it must leave
the database in a valid or consistent
state that satisfies all the constraints
specified on the database schema
database administrators in any
organization
where many people use the same resources
there is a need for a chief
administrator to oversee and manage
these resources in a database
environment the primary resource is the
database itself and the secondary
resource is the DBMS and related
software when a relational database is
to be designed and developed as a
requirements of the database and its
processing becomes better understood the
data that we want to keep about each
entity within an entity type is
contained in attributes and attribute is
some quality about the entities that we
are interested in and want to hold on
the database an attribute that is used
to identify each entity from all the
others in the entity type this attribute
is known as the primary key the final
element is the relationship type real
world entities have relationships
between them and relationships between
entities on the entity relationship
there can be more than one type of
relationship between entities summary
now in the end let us summarize what we
have learnt in this lecture dbmss
are the technology tools that directly
support managing organizational data the
DBMS provides a set of operations or a
language called the data manipulation
language DML for these purposes when
multiple users share a large database it
is likely that most users will not be
authorized to access all information in
the database database systems must
provide capabilities for efficiently
executing queries and updates because
the database is typically stored on disk
the DBMS must provide specialized data
structures and search techniques to
speed up disk search for the desired
records