COMP 207 Database development and design

www.csc.liv.ac.uk/~khan/COMP207.html

M S Khan Room G.22

Dept of computer science University of Liverpool [email protected]

What is this module about?

In COMP 102 you learn the basics of relational databases. Here we focus on: • Database design principles for ER models: • Logical and physical layer • Transaction models • Concurrency • Recoverability • Object oriented models • Semi structured models 2

Prerequisites

• Entity relationship (E/R) modelling • Relational data model • Good knowledge of SQL 3

Content of the course

Part 1: Revise basic notions of relational Databases Part 2: Advanced database design: Normalisation, Logical and Physical DB design methodologies; Part 3: Transaction management; Part 4: Overview on Object Oriented and Object Relational databases; Part 5: Semi-structured models: XML; Part 6: Data Mining.

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Aims

To introduce students to: • a systematic design approach to developing databases, including the use of normalisation; • the problems arising from concurrency in databases, and how they are solved; • the problems involved in the integration of heterogeneous sources of information and semi structured data; • non-relational databases; • techniques for analyzing large amounts of data.

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Learning outcomes

At the conclusion of this module, students should: • understand the principles of the relational database model.

• understand the design process underlying the design of databases and the use of normalization; • understand the concepts involved in transaction management; • understand the XML terminology and syntax and understand how to use XML; • understand OODBS and their advantages and disadvantages to relational DBS; • understand basic concepts of data mining; 6

Textbooks

• • • Connolly & Begg. “Database systems”. Addison Wesley (fifth edition); R. Elmasri, S.B. Navathe. “Fundamentals of Database Systems” (third edition) Addison Wesley; H. Garcia-Molina, J.D.Ullman, J Widom "Database systems. The complete book”. Prentice Hall (First or Second Edition); Useful readings: • J.D.Ullman, J Widom ”A First Course in Database Systems" Prentice Hall (ThirdEdition); • Silberschatz, Korth and Sudarshan. “Database System Concepts” McGraw-Hill • N. Shah, "Database Systems using Oracle", Prentice Hall 7

Assessment weightings

• 80% Exam; •

Note - all of material covered by the module is relevant, and thus any of it could appear in the exam...!

• 20% Coursework; 1. The coursework will consist of two assignments, most probably one in week 5 and the other in week 9; 2. There are 4 lab slots available, in order to avoid conflicts with lectures: 3. The lab slots can also be used to access the weekly exercises on Vital!

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Module Delivery

Lecture Times: – Tuesday 12:00 (SHER-LT1) – Thursday 13:00 (CHAD-LT CHAD) – Friday 09:00 (SHER-LT1) Lab Classes: – Formal Labs (with exercises) weekly at: – Thursdays: 09:00 – 10:00 and 10:00 – 11:00 – Fridays: 10:00 – 11:00 and 11:00 – 12:00 – Commence in Week 3 in Lab 3, Holt Building – Check the course website to see which class you’re in

Resources

Printouts of the lecture notes will be available from the Computer Science Helpdesk – This module will evolve as the module proceeds. Whilst we will strive to adhere to the made available at the beginning of the module (lecture 3), these

may vary slightly from the slides delivered.

Additional or amended notes will appear on the web after each lecture.

Exercises, and answer to common questions will be posted on Vital.

Expectations

The field of Databases is vast and still evolving: – Exams and Exercise questions rely on

understanding

and

applying

much of the material in this module.

– Don’t rely on simply remembering the notes, as this won’t help you pass...!

Finally...

The obvious...

– Switch off all mobile phones during lectures – Remember to sign the register – Do not sign the register on behalf of others – Attend lectures and attempt the exercises set – – this will help you pass the exam – Attend the practical classes – these will help you do the coursework – Ask questions if there is anything that you do not understand – If you can’t hear me in the back, let me know!

And respect your fellow students...

– There are people here who want to learn!

– If you want to talk or mess around, then don’t bother attending!

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Lecture 1

Introduction to Databases

Examples of Database Applications

Purchases from the supermarket:

Queries for stock, prices, etc

Purchases using your credit card:

Queries for credit limit, available credit…

Booking a holiday at the travel agents Using the local library Taking out insurance Renting a video Using the Internet: Amazon, Itunes… Studying at university

File-Based Systems

Collection of application programs that perform services for the end users (e.g. reports). Each program defines and manages its own data.

• Programmers need to write routines to: Enter new data (in the right position); Update data making sure that no inconsistencies arise; Delete data; Query the relevant data; Make sure changes are propagated throughout the file!

Limitations of File-Based Approach

Separation and isolation of data • Each program maintains its own set of data: – Spider and Tulip would maintain separate data!

• Users of one program may be unaware of potentially useful data held by other programs.

Duplication of data • Same data is held by different programs.

• Wasted space and potentially different values and/or different formats for the same item – Loss of data integrity

Limitations of File-Based Approach

Data dependence • File structure is defined in the program code: – Every change in format requires reading the original file, adding a new record to a temporary file (with the modified data), repeat this for every record! Then delete the original file and rename the temporary file … Lots of work.

Incompatible file formats • Programs are written in different languages, and so cannot easily access each other’s files.

– Makes the integration of different applications difficul t Fixed Queries/Proliferation of application programs • Programs are written to satisfy particular functions.

• Any new requirement needs a new program.

• Access restricted to one user at a time.

Database Approach

Arose because: • Definition of data was embedded in application programs, rather than being stored separately and independently.

• No control over access and manipulation of data beyond that imposed by application programs.

Result: • the database and Database Management System (DBMS).

We will look at many DBMS functionalities, such as transaction management, recoverability, etc …

Database

Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization: • From disconnected files with redundant data to integrated data items with minimum amount of duplication System catalog (metadata) provides description of data to enable program –data independence.

Logically related data comprises entities, attributes, and relationships of an organization’s information.

Database Management System (DBMS)

A software system that enables users to define, create, maintain, and control access to the database: • Allows the definition of the DB and its constraints (Data Definition Language); • Allows the update, deletion and retrieval of data (Data Manipulation Language); In relational databases SQL is both the DDL and the DML.

( Database) application program : a computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS.

Database Approach

Data definition language (DDL).

• Permits specification of data types, structures and any data constraints. • All specifications are stored in the database.

Data manipulation language (DML).

• General enquiry facility (query language) of the data.

Database Approach The DBMS provides controlled access to database including:

• a security system • an integrity system • a concurrency control system • a recovery control system • a user-accessible catalog.

Views

Allows each user to have his or her own view of the database.

A view is essentially some subset of the database.

Views - Benefits

Reduce complexity: • Users see only the data they are interested in; Provide a level of security: • Data is excluded from what a user can access; Provide a mechanism to customize the appearance of the database: • Allows users to change to rename data; Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed

Components of DBMS Environment

Components of DBMS Environment

Hardware • Can range from a PC to a network of computers.

Software • DBMS, operating system, network software (if necessary) and also the application programs.

Data • Used by the organization and a description of this data called the schema.

Components of DBMS Environment

Procedures • Instructions and rules that should be applied to the design and use of the database and DBMS.

People

Roles in the Database Environment

Data Administrator (DA) Database Administrator (DBA) Database Designers (Logical and Physical) Application Programmers End Users (naive and sophisticated)

History of Database Systems

First-generation • Hierarchical and Network Second generation • Relational Third generation • • Object-Relational Object-Oriented

Advantages of DBMSs

Control of data redundancy Data consistency More information from the same amount of data Sharing of data Improved data integrity Improved security Enforcement of standards Economy of scale

Advantages of DBMSs

Balance conflicting requirements Improved data accessibility and responsiveness Increased productivity Improved maintenance through data independence Increased concurrency Improved backup and recovery services

Disadvantages of DBMSs

Complexity Size Cost of DBMS Additional hardware costs Cost of conversion Performance Higher impact of a failure