Download Summary of the main concepts of DBMS (Part 1)

Summary of the main concepts of DBMS (Part 1)
Summary of the main concepts of DBMS (Part 1)
Prepared by: Mahmoud Rafeek Alfarra
Lecturer in CST- Khan younis
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Data is a stored representation of meaningful objects and events, as
Mahmoud, Ali, Apple, car, Exam, Football Match.
Data can be one of two categories
 Structured: This can be formatted as numbers, text, dates.
 Unstructured: This can't be formatted as images, video,
documents, audio.
Information is a processed data to increase knowledge in the person
using the data.
Database is an organized collection of logically related data.
Metadata (data dictionary, system catalog, data about): data that
describes the properties and context of user data.
Prepared by: Mahmoud Rafeek Alfarra
Lecturer in CST- Khan younis
March 2011
1
Summary of the main concepts of DBMS (Part 1)
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Database Management System(DBMS) is a software system that is used
to create, maintain, and provide controlled access to user databases
DBMS
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DBMS manages data resources like an operating system manages
hardware resources.
Components of the database environment:
Prepared by: Mahmoud Rafeek Alfarra
Lecturer in CST- Khan younis
March 2011
Summary of the main concepts of DBMS (Part 1)
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Data base support Multiple Views of the Data by derived many views
(which is a subset of the database but is not explicitly stored).
 Multiple users can access the database at the same time
(which is the concurrency control software: Ensure that several
users trying to update the same data do so in a controlled
manner)
 Using transaction which is executing program or process that
includes one or more database operations, has two properties:
 Isolation property: transaction not related to others
 Atomicity property: Either all the database operations in
a transaction are executed or none are.
Three-Schema Architecture:
 Internal level : Describes physical storage structure of the
database
 Conceptual level: Describes structure of the whole database for
a community of users
 External or view level: Describes part of the database that a
particular user group is interested in.
Prepared by: Mahmoud Rafeek Alfarra
Lecturer in CST- Khan younis
March 2011
Summary of the main concepts of DBMS (Part 1)
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Phases of designing a database: designing data base means how the
data base will be built in the different steps which are (External,
internal).
1. External schema contains two steps which are (Requirements
specification and analysis) and (Conceptual design) which
includes identification of important entity and relationship that is
what is the data to be represented.
2. Internal Schema contains two designing steps which are (Logical
design) and (Physical design).
 Logical design: To translate the conceptual representation
to the logical structure of the database, this includes the
designing of relations.
 Physical design: To allow the designer to decide how the
logical structure is to be physically implemented on the
target DBMS (How is the data stored in memory?).
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The conceptual representation of data does not include details of how
data is stored or how operations are implemented.
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Data model: An integrated collection of concepts for describing data,
relationships between data, and constrains on the data in an
organization. (Representation of the data base steps )
Categories of Data Models:
 Relational data model
 Object data model
 Physical data models
Database schema: the overall description of the database.
(According to 3-arch.)
 External schema: multiple
 conceptual schema: one (data items & relation)
 internal schema: one (contains the stored procedure and
method)
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Prepared by: Mahmoud Rafeek Alfarra
Lecturer in CST- Khan younis
March 2011
4
Summary of the main concepts of DBMS (Part 1)
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DBMS is responsible for mapping between these three types of
schema.
DBMS Languages
 Data definition language (DDL): Defines both schemas
 Storage definition language (SDL): Specifies the internal schema
 View definition language (VDL): Specifies user views/mappings
to conceptual schema
 Data manipulation language (DML): Allows retrieval, insertion,
deletion, modification.
Prepared by: Mahmoud Rafeek Alfarra
Lecturer in CST- Khan younis
March 2011
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