Database

DATABASE

Neenu Prasad

Definition
• Data: facts that can be recorded and that have implicit
meaning.

• A database is a collection of interrelated data , typically
describing the activities of one or more related

Organizations and is used for managing large bodies of
information. #

Example
• A university database might contain information about the
following:

• Entities such as students, faculty, courses, and classrooms.
• Relationships between entities, such as students' enrolment in

courses, faculty teaching courses, and the use of rooms for
courses #

DATABASE MANAGEMENT SYSTEMS(DBMS)
• general-purpose software system
• Collection of inter related data programs to manage the data.

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Well known DBMS
• • • • • • • Oracle IBM DB2 Microsoft SQL Server Microsoft Access PostgreSQL MySQL SQLite
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Users
• Users are differentiated by the way they expect to interact
with the system..

• Naïve users :
They invoke one of the permanent application programs that

have been written previously.

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Users
• Sophisticated users : They form requests in a database query language.ie they interact with the systems without writing application

programs.
• Application programmers : They are computer professionals who write the application programs. They can choose from many tools to develop user interfaces #

Database Administrator (DBA)
• Coordinates all the activities of the database system.

• good understanding of the enterprise’s information
resources and needs.

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Functions of DBA
• Schema definition

• Storage structure and access method definition
• Schema and physical organization modification • Granting user authority to access the database • Specifying integrity constraints • Acting as liaison with users

• Monitoring performance and responding to changes in
requirements #

Query Processing
• It includes 1. Parsing and translation 2. Optimization 3. Evaluation

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Cont…
a) DDL Interpreter (Parsing and Translation): Interprets the DDL statements and records the definition in the data

dictionary. Data dictionary is a special type of table that can be accessed
and modified only by the DB itself. b) DML Complier (Query Optimisation):

Translates DML statements into an evaluation plan consisting of low level
instruction that query evaluation engine understand. c) Query Evaluation Engine (evaluation):

Executes the low level instructions generated by DML compiler.

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Storage Manager
• program module that provides the interface between the

low level data stored in db and application programs and
queries submitted to the system.

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Storage Manager
• Authorisation and integrity manager They performs tests for satisfaction of integrity constraints and checks for the authority of users to access data. • Transaction manager

Ensures that the database remains in a consistent state.
• File manager Manages the allocation of space on disk storage and the structures used

to represent information stored on disk.
• Buffer Manager Responsible for fetching data from disk storage into main memory

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APPLICATIONS OF DATABASES
• Banking: all transactions • Airlines: reservations, schedules • Universities: registration, grades

• Sales: customers, products, purchases
• Online retailers: order tracking, customized recommendations • Manufacturing: production, inventory, orders, supply chain #

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