Database management system basic, database, database management, learn database, database system

BASIC CONCEPTS
1. What is a database?
A database is a collection of interrelaated data which can be
used:
• alone, or
• combined / related to other data
to provide answers to the user’s question.
2.What is Database Management System?
A database management system (DBMS) is system software for
creating and managing databases. The DBMS provides users and
programmers with a systematic way to create, retrieve, update and
manage data.

1. Retrieve data that are both convenient and
efficient
2. Safety of information stored in DBMS .
3. Avoid possible anomalous result.

a) BANK :For customer ,informaion , account,and loans, and
transaction.
b) Airline: For reservation and schedule information. Airline were
among the first to use database in a geographically distributed
manner terminals situated around the world accessed the central
database system through phone lines and other data network.
c) Universities: For students information, course registration, and
grades.
d) Credits card transaction: For purchases on credits cards and
generation of monthly statements.
e) Sales: For customer, product, and purchase information.
e) Human resources: For information about employees, salaries,
payroll taxes and benefits, and for generation of paychecks.

a) Data redundancy and inconsistency
b) Difficulty in accessing data
c) Data isolation
d) Integrity problems
e) Atomicity problems
f) Concurrent-access anomalies
g) Security problems

1 DATA ABSTRACTION
• Physical Level: The lowest level of abstraction
describeshow the data are actually stored.
• Logical Level: The next –higher level of abstraction
describes what data are actually stored in the database, and
what relationship exist among those data.
• View Level: The highest level of abstraction describes
only part of the entire database.

View of data
View 1 View 2 View n
Logical level
Physical level

* Reduction of Redundancies: Centralized control of data by the
DBA avoids unnecessary duplication of data and effectively reduces
the total amount of data storage required.
*Elimination of Inconsistencies: The main advantage of
avoiding duplication is the elimination of inconsistencies that tend to
be present in redundant data files.

* Integrity: Centralized control can also ensure that adequate checks
are incorporated in the DBMS to provide data integrity.
*Data Independence: Data independence is usually considered from
two points of view: physical data independence and logical data
independence.
*Shared Data: A database allows the sharing of data under its control
by any number of application programs or users

Database management system basic, database, database management, learn database, database system

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