Download Introduction to Databases Lecture 1 Chapters 1 - 2 Robb T. Koether

Introduction to Databases
Lecture 1
Chapters 1 - 2
Robb T. Koether
Hampden-Sydney College
Wed, Jan 15, 2014
Robb T. Koether (Hampden-Sydney College)
Introduction to Databases
Wed, Jan 15, 2014
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1
Overview of the Course
2
Databases
3
Benefits of Databases
4
The Concurrency Problem
5
Assignment
Robb T. Koether (Hampden-Sydney College)
Introduction to Databases
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Outline
1
Overview of the Course
2
Databases
3
Benefits of Databases
4
The Concurrency Problem
5
Assignment
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Introduction to Databases
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Overview of the Course
Relational databases
Basics
Normal forms
Triggers
Views
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Introduction to Databases
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Overview of the Course
Dynamic web pages
HTML
CSS
PHP
Javascript
AJAX
JQuery
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Overview of the Course
Semistructured databases
XML
XPath
XSLT
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Introduction to Databases
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Project
Develop a social network application for the web.
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Introduction to Databases
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Outline
1
Overview of the Course
2
Databases
3
Benefits of Databases
4
The Concurrency Problem
5
Assignment
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Introduction to Databases
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Databases
Definition (Database)
A database (DB) is a collection of related data.
Definition (Database Management System)
A database management system (DBMS) is a program that accepts
queries into a database and returns responses.
Definition (Query)
A query is a request that is sent to a DBMS instructing it to perform an
operation on a database. A query may retrieve, insert, delete, or
update data in the database.
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Databases
Query
User
Robb T. Koether (Hampden-Sydney College)
DBMS
Introduction to Databases
Optimized
query
Database
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Databases
Response
User
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Response
DBMS
Introduction to Databases
Database
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Databases
Characteristics of a DBMS.
Limited redundancy
Restricted access (privileges and views)
Persistent storage
Efficiency
Backup and recovery
Multiple users (concurrency)
Data integrity
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Introduction to Databases
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Databases
As we will see, it can be quite tedious to enter the queries through
a command line.
Often the “user” is actually an application program or a webpage,
in which the queries are preprogrammed.
After our initial study of databases, we will design webpages that
will automatically query the underlying database.
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Introduction to Databases
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Outline
1
Overview of the Course
2
Databases
3
Benefits of Databases
4
The Concurrency Problem
5
Assignment
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Introduction to Databases
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Benefits of Databases
A few of the benefits of using a database:
The user does not need to have knowledge of how the data is
stored. He works through a user-friendly interface.
Different users can be given different views of the data. Each user
may be unaware of the views that other users have.
Data can be easily shared among users.
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Introduction to Databases
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Benefits of Databases
Online
Catalog
Sales
Records
Inventory
Customer
Salesman
Manager
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Benefits of Databases
Comprehensive
Database
(Catalog, Sales,
Inventory)
Customer
Salesman
Manager
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Introduction to Databases
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Various Roles
Roles of various individuals involved.
The database administrator (DBA) – Oversees the entire system.
The database designer – Designs a database to meet the specs.
The user – Queries the database according to his needs.
At various times in this course, we will be the database designer
and the database user.
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Various Roles
Roles of various individuals involved.
The database administrator (DBA) – Oversees the entire system.
The database designer – Designs a database to meet the specs.
The user – Queries the database according to his needs.
At various times in this course, we will be the database designer
and the database user.
One other person involved is the person who built the DBMS.
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Introduction to Databases
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Outline
1
Overview of the Course
2
Databases
3
Benefits of Databases
4
The Concurrency Problem
5
Assignment
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Introduction to Databases
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Concurrency
Multiple users accessing the very same data at the very same
time leads to the concurrency problem.
For example, Alice, a customer, requests the price of item #123.
At the very same time, Bob, an employee, is updating the price of
item #123.
Which price will Alice see?
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Introduction to Databases
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Concurrency
Multiple users accessing the very same data at the very same
time leads to the concurrency problem.
For example, Alice, a customer, requests the price of item #123.
At the very same time, Bob, an employee, is updating the price of
item #123.
Which price will Alice see?
It depends on who goes first, Alice or Bob.
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Introduction to Databases
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Concurrency
More significantly, Alice, an airline employee goes online to select
a list of passengers on flight #123.
At the very same time, Bob, another airline employee, goes online
to change the flight number from #123 to #456.
Alice selects the first 50 names of passengers on flight #123.
At that moment, the flight number is changed to #456.
The last 50 names are not selected because the flight number
was no longer #123.
This type of conflict must be avoided.
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OLAP
Definition (Database)
Online analytical processing (OLAP) involves querying a database to
obtain summary data, typical retrievals and aggregation.
Most database applications fall into one of two categories: OLAP
or OLTP.
A typical OLAP application would be to get the total daily sales
from online purchases.
OLAP is computationally intensive (e.g., summing over millions of
records).
This is more like what we will do when we first study databases.
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Introduction to Databases
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OLTP
Definition (Database)
Online transaction processing (OLTP) involves many small queries,
typically insertions.
A typical OLTP application would be a database of online
purchases. Each purchase is inserted into the database.
OLTP is not computationally intensive.
This is more like what we will do with PHP and Javascript.
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Outline
1
Overview of the Course
2
Databases
3
Benefits of Databases
4
The Concurrency Problem
5
Assignment
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Introduction to Databases
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Assignment
Read Chapter 1 - Databases and Database Users.
Read Chapter 2 - Database System Concepts and Architecture.
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