1.Fundamentals of DBMS
Data is the most important
component in any work that we do.
Data means collection of
information or collection of raw facts.
Data Base is a collection of
related data.
Data Base Management System is the management
system or maintenance system on databases.
(Or)
It is a suit of software program for
creating, maintaining & manipulating the data in database. (Or)
It allows the users to insert the data, to
retrieve the data, to modify the data and to delete the data.
The first databases of kind existed in the
form of files.
A file is nothing but collection of records.
A Record is nothing but collection of
information or data.
But the file system was not very efficient
.it was crippled by slow data search speed. It includes the following
Drawbacks.
1.Security
2.Data Redundancy
3.Data Integrity
4.Concurrency Control
5.Slow in Process
Security:
No Login name No Password.
Data
Redundancy: Data reputation or data duplication is very high.
Data
Integrity: No Data Validation process.
Concurrency
Control: No control in files system when concurrency exists.
Slow
in process: File System follows Sequential-searching process.
Data Base System models or Types of DBMS
1. HIERARCHICAL
MODEL
2. NETWORK
MODEL
3. RELATIONAL
MODEL
Hierarchical Model or HDMS:
One
of the earliest database management systems was based on the Hierarchical
model. Here data can be organized in the form of tree structure or
level-by-level manner with one limitation that is “every sub node or child node should have only one parent node”.
It is very simple in structure
Based on the limitation Cross communication is not possible.
There is chance of Data redundancy.
Network Model or NDBMS:
To
overcome the problems proposed by the hierarchical data model, the network data
model was developed. It is also known as communication oriented database
management system. Cross communication is possible in NDBMS.
Here data can be organized in the form of
tree structure or level by level manner with cross communication. It cannot
provide proper query facility, so that we have to write big programs even for
small operation. It is complex in structure.
Relational DBMS:
RDBMS are most important database systems used in the
software industry today. It was Exclusively used to establish the relation ship
between two-database objects. One of the
database objects is one table.
The Relation ship may be
One – One 1:1
One – Many 1:M
Many-One M: 1
Many-Many M: M
Entity-Relationship Model(E-R Model):
An Entity is nothing but an object, which is physically
existed in the real world.
Ex: car, computer, chair
An Object in the database is a table so that an entity is nothing
but a table.
Every Entity contains characters specifies its attribute
simply it is a column in the table.
E-R Model is used to establish the relationship between two
tables in pictorial format. It provides the following components.
Rectangle
for representing Object/Table/Entity
Ellipse
for representing Attribute/Column
Rhombus for representing Relationship
E.g.:
Loan
Customer
Loanid
Cno Cname LType City
Amt
 |
||||
 |
||||
 |
||||
One-One
One-Many
Many-One
|
Many - Many
FEATURES OF RELATIONAL DBMS:
1. DATA IS STORED IN TABLES.
2. INTERSECTION OF ROWS AND
COLUMNS WILL GIVE ONLY ONE VALUE.
3. RELATION AMONG DATA IS
ESTABLISHED LOGICALLY.
4. THERE IS NO PHYSICAL LINK
AMONG DATA
5. THERE IS NO DATA REDUNDANCY
6. HIGH SECURITY FOR DATA
7. IT SUPPORTS ANY TYPE OF DATA
(EX: NUMBERS, NUMERIC, DATA, CHARACTER, DATE IMAGES ETC).
8. IT SUPPORTS NULL VALUES.
9. SUPPORT CODD RULES
10. IT SUPPORTS INTEGRITY
CONSTRAINTS
11. MULTIPLE USERS CAN ACCESS
DATA FROM ANY LOCATION.
Difference Between DBMS and RDBMS
|
DBMS
|
RDBMS
|
|
No
relation ship concept
|
Exclusively
Designed for Relationship
|
|
Single
user support
|
Multiple
user support
|
|
Supports
3 rules of E.F.Codd
|
Supports
6 rules of E.F.Codd
|
|
It
treats its data as files internally
|
It
treats its data as Tables internally
|
|
Requires
low software and hardware
|
Requires
high software and hardware
|
|
Ex:
|
Ex:
|
No comments:
Post a Comment