Презентация «Introduction to Database Systems»

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Презентация «Introduction to Database Systems»

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Introduction to Database Systems Database Systems Lecture 5
Introduction to Database Systems Database Systems Lecture 5
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Textbook Recommended textbooks: ‘Database Systems: A practical approach to design, implementation an
Textbook Recommended textbooks: ‘Database Systems: A practical approach to design, implementation and management’ by Connolly and Begg `A first course in database systems’ by Ullman and Widom.
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Why Study Databases? Databases are useful Many computing applications deal with large amounts of inf
Why Study Databases? Databases are useful Many computing applications deal with large amounts of information Database systems give a set of tools for storing, searching and managing this information
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What is a Database? “A set of information held in a computer” Oxford English Dictionary “One or more
What is a Database? “A set of information held in a computer” Oxford English Dictionary “One or more large structured sets of persistent data, usually associated with software to update and query the …
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Databases Web indexes Library catalogues Medical records Bank accounts Stock control Personnel syste
Databases Web indexes Library catalogues Medical records Bank accounts Stock control Personnel systems Product catalogues Telephone directories
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Database Systems A database system consists of Data (the database) Software Hardware Users We focus
Database Systems A database system consists of Data (the database) Software Hardware Users We focus mainly on the software
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Database Users End users Use the database system to achieve some goal Application developers Write s
Database Users End users Use the database system to achieve some goal Application developers Write software to allow end users to interface with the database system
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Database Management Systems A database is a collection of information A database management system (
Database Management Systems A database is a collection of information A database management system (DBMS) is the software than controls that information
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What the DBMS does Provides users with Data definition language (DDL) Data manipulation language (DM
What the DBMS does Provides users with Data definition language (DDL) Data manipulation language (DML) Data control language (DCL) Often these are all the same language
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Data Dictionary - Metadata The dictionary or catalog stores information about the database itself Th
Data Dictionary - Metadata The dictionary or catalog stores information about the database itself This is data about data or ‘metadata’ Almost every aspect of the DBMS uses the dictionary
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File Based Systems File based systems Data is stored in files Each file has a specific format Progra
File Based Systems File based systems Data is stored in files Each file has a specific format Programs that use these files depend on knowledge about that format
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Relational Systems Problems with early databases Navigating the records requires complex programs Th
Relational Systems Problems with early databases Navigating the records requires complex programs There is minimal data independence No theoretical foundations
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Relational Systems Information is stored as tuples or records in relations or tables There is a soun
Relational Systems Information is stored as tuples or records in relations or tables There is a sound mathematical theory of relations Most modern DBMS are based on the relational model
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ANSI/SPARC Architecture ANSI - American National Standards Institute SPARC - Standards Planning and
ANSI/SPARC Architecture ANSI - American National Standards Institute SPARC - Standards Planning and Requirements Committee 1975 - proposed a framework for DBs
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Internal Level Deals with physical storage of data Structure of records on disk - files, pages, bloc
Internal Level Deals with physical storage of data Structure of records on disk - files, pages, blocks Indexes and ordering of records Used by database system programmers
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Conceptual Level Deals with the organisation of the data as a whole Abstractions are used to remove
Conceptual Level Deals with the organisation of the data as a whole Abstractions are used to remove unnecessary details of the internal level Used by DBAs and application programmers
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External Level Provides a view of the database tailored to a user Parts of the data may be hidden Da
External Level Provides a view of the database tailored to a user Parts of the data may be hidden Data is presented in a useful form Used by end users and application programmers
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Mappings Mappings translate information from one level to the next External/Conceptual Conceptual/In
Mappings Mappings translate information from one level to the next External/Conceptual Conceptual/Internal These mappings provide data independence
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ANSI/SPARC Architecture
ANSI/SPARC Architecture
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This Lecture in Exams Describe the three levels of the ANSI/SPARC model. You should include informat
This Lecture in Exams Describe the three levels of the ANSI/SPARC model. You should include information about what each level is for, which users might be interested in which levels, and how the …
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Next Lecture The Relational Model Relational data structure Relational data integrity Relational dat
Next Lecture The Relational Model Relational data structure Relational data integrity Relational data manipulation For more information Connolly and Begg chapters 3 and 4 Ullman and Widom (2 ed. ) …


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