Dbms slides

 APPLICATIONS
 FILE SYSTEM
 VIEW OF DATA
 QUERY PROCESSOR
 DATABASE USERS AND ADMINISTRATORS
 DATA LANGUAGES
 TRANSACTION MANAGEMENT
 STORAGE MANAGER
 DATA MODELS

APPLICATION
a) BANKING: 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.
f) Human resources: For information about employees, salaries,
payroll taxes and benefits, and for generation of paychecks.

VIEW OF DATA
1. DATA ABSTRACTION
• Physical Level: The lowest level of abstraction describes
how 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 level

View 1 View 2 View n

Logical level

Physical level

(The three levels of data abstraction)

INSTANCES AND SCHEMAS: The collection of
information stored in the database at a particular moment is
called an instance of the database. The overall design of the
database is called the database schema.

QUERY PROCESSOR
The query processor components includes:
• DDL interpreter: Which interprets DDL statements and
records the definitions in the data dictionary.
• DML: Compiler which translates DML statements in a
query language into an evaluation plan consisting of low-
Level instructions that the evaluation engine understands.
• Query evaluation engine: Which executes low-level
instruction generates by the DML compiler.

Database Users and
Administrators
• Database users and user interfaces
 Naive Users
 Application Programmers
 Sophisticated Users
 Online analytical processing(ONLP)
 Specialized Users

• Database Administrator
 Schema definition
 Storage structure and access-method definition
 Schema and physical-organization modification
 Granting of authorization for data access
 Routine maintenance

DATA LANGUAGES
The database provides a data definition
Language to specify the database schema and a data
Manipulation language to express database queries
and updates.

• DATA-DEFINITION LANGUAGE

• DATA-MANIPULATION

DATA-DEFINITION LANGUAGE(DDL): We
specify a database schema by a set of definition expressed
by a special language called a Data-Definition Language.
For instance, the following statement in the SQL
language defines the account table:

e.g. create table account(account-number
char (10),balance integer)
Execution of the above DDL statement create the
account table. In addition, it updates a special set of
tables called the DATA DICTIONARY or DATA
DIRECTORY

DATA-MANIPULATION LANGUAGE: Data
manipulation is:
• The retrieval of information stored in the
database.
• The insertion of new information into the
database.
• The deletion of information from the database.
• The modification of information stored in the
database.

A data-manipulation language(DML) is a
language that enables users to access or manipulate
data as organized by the appropriate data model. There
are basically two types :

• Procedural DMLs

• Declarative DMLs
The query in the SQL language finds the name
of the customer whose customer-id is 1999:

e.g. Select customer.customer-name
from customer
where customer.customer-id=1999

TRANSACTION
MANAGEMENT
A transaction is a collection of operations that
performs a single logical function in a database
application. Each transaction is a unit of both atomicity
and consistency . Thus, we require that transaction do
not violate any database-consistency constraints. That
is, if the database was consistent when a transaction
started, the database must be consistent when the
transaction successfully terminates.

STORAGE MANAGER
A storage is a program module that provides the
interface between the low-level data stored in the database
and the application program and queries submitted to the
system. The storage manager . The storage manager is
responsible for the interaction with the file manager . The
row data are stored on the disk using the file system, which
is usually provided by a conventional operating system.
The storage manager translates the various DML
statements into low-level file-system commands. Thus, the
storage manager is responsible for storing, retrieving and
updating in the database.

Dbms slides

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Dbms slides