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					Websites and Databases

Chapter 3 – Developing Websites
Part 4
                       What is a Database?
 A database (DB) is a computerised collection of
  data…

 … typically organized to make common
  retrievals of information easy and efficient.

 A database management system (DBMS) is
  the software mechanism for managing that data.
                           Database Origins
 Databases were created (originally in the
  1960s) to solve problems with file-oriented
  systems by being:
     Compact
     Fast and easy to use
     Current
     Accurate
     Secure
     Allowing the easy sharing of data between
      multiple users
               Databases for Websites

 Databases have quickly become integral
  to the design, development, and services
  offered by web sites.

 Consider sites like Amazon.com that must
  be able to allow users to quickly jump
  through a vast virtual warehouse of books
  and compact disks.
Databases for Websites




www.amazon.com
                Databases for Websites
 How could Amazon.com create web pages
  for every single item in their inventory and
  how could they keep all those pages up-
  to-date?

 Their web pages are created on-the-fly by
  a program that "queries" a database of
  inventory items and produces an HTML
  page based on the results of that query.
                     Database Complexity
 Database complexity varies according to the
  system it is being used for.

 A database can be as complex and demanding
  as an account tracking system used by a bank
  for managing changing accounts of thousands of
  clients…

 … or as simple as a collection of electronic
  business cards on your laptop.
                   Database Complexity

 Yet, the most important thing is that its
  DBMS allows you to store data and get it
  or modify it when you need to easily and
  efficiently, regardless of the amount of
  data being manipulated.

 What the data is and how demanding you
  will be when retrieving and modifying that
  data is simply a matter of scale (or size).
                                DBMS Types

 There are two DBMS types:
     Industrial
        Oracle
        Microsoft SQL Server
        MySQL


     Home
        Dbase
        FoxPro
        Microsoft Access
                               Industrial DBMS
 Industrial DBMSs are used to store huge
  amounts of data…

 … and process thousands of transactions and
  stored procedures.

 Did you know?
     MS SQL Server was Microsoft’s response to Oracle…
     … while MySQL was Linux’s marketing response to
      MS SQL Server!
                                   Home DBMS
 Although MS Access is just a Home DB, it is
  also used for small enterprises…

 … however one must keep in mind that it has
  huge limitations for industrial use.

 On the other hand, given that normal users are
  so familiar with it, Access is preferred as a front
  end to the bigger DBMS in offices.

 This is usually because users do not need initial
  training on it and is simple to use.
                                   Database Types

 There are two main DB types:
     Analytic Databases
        Also known as OLAP
         (On-Line Analytical Processing)
       Primarily static, read-only databases which store
         archived, historical data used for analysis.
     Operational Databases
        Also known as OLTP
         (On-Line Transactional Processing)
       Used to manage more dynamic bits of data. They allow
         you to modify that data (add, change or delete data).
                              What is SQL?
 SQL is a standard computer language for
  accessing and manipulating databases.

 Stands for Structured Query Language.

 Allows you to access a database.

 Is an ANSI standard computer language.

 Is easy to learn.
                                     SQL Queries
 SQL is a syntax for executing queries. But the
  SQL language also includes a syntax to update,
  insert, and delete records.

 These query and update commands together
  form the Data Manipulation Language (DML)
  part of SQL:
     SELECT – extracts data from a DB table
     UPDATE – updates data in a DB table
     DELETE – deletes data from a DB table
     INSERT INTO – inserts new data into a DB table
                                Database Tables
 A database most often contains one or more
  tables.

 Each table is identified by a name.
     e.g. "Customers" or "Orders"


 Tables contain records (rows) with data.

 Data can also be identified by the field (column)
  that it falls under.
                 Database Tables (cont.)
 It is important to note that how or where the
  tables of data are stored makes no difference.

 Each table can be identified by a unique name
  and that name can be used by the database to
  find the table behind the scenes.

 As a user, all you need to know is the table
  name in order to use it. You do not need to
  worry about the complexities of how the data is
  stored on the hard drive.
                                    Example:
                              Tables and SQL
 Below is an example of a table called "Persons":




 How many records and fields does the table
  contain?
 What does the following SQL statement do?
                  Client-Server Database

 A database server is left running 24 hours a
  day, and 7 days a week – like this, the server
  can handle database requests at any hour.

 Database requests come in from "clients" who
  access the database through its command line
  interface or by connecting to a database
  socket.

 Requests are handled as they come in and
  multiple requests can be handled at one time.
                  Client-Server Database

 For web applications which must be available for
  world wide time zone usage, it is essential to
  build upon a client/server database which can
  run all the time.

 Hopefully, you will also choose a database with
  full functionality such as security and
  concurrency control (making sure that two users
  cannot simultaneously change a record).
                                   Summary…
 Dynamic websites typically generate web pages
  on-the-fly by making use of a back-end
  database.

 A database is a store of structured data.

 A database management system is a software
  application used to manage data stored in some
  database.
                                  Summary…
 DBMS types include MS SQL Server, MySQL
  and Oracle for industrial purposes…

 … while MS Access is usually used for home
  use or as a front-end for small enterprises.

 DBMSs use SQL statements to be able to
  query a database for information.
                                         Summary…
 DB types include OLAP and OLTP.

 On-Line Analytical Processing: one can only
  read/view archived data in a DB
     SELECT statements only are used.

 On-Line Transactional Processing: one can
  read/view, add, modify and delete data in a DB
     SELECT, INSERT INTO, UPDATE and DELETE
      statements are used.
                                               References
 Sol, S., “Introduction to Databases for the Web: Pt. 1”, 1998,
  [Online]
  http://www.databasejournal.com/sqletc/article.php/26861_1428721_
  1

 W3 Schools, “SQL Introduction”, 2005, [Online]
  http://www.w3schools.com/sql/sql_intro.asp

				
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posted:4/27/2013
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