Creating Web Databases'

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Creating Web Databases.

• Part 1.

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Persistent Data.

• Web applications remember your setting by means
  of a database linked to the site.

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Central Sales Database.

• A site such as Amazon has a central data store
  and users may browse the content from different
  locations.

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To set this up we need two things

• A Database Management System.
• Some sort of data aware objects.

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Database Management Systems.

• For a commercial web site the following are
  examples of suitable Database Management Systems
  (DBMS).
• MySQL
• An open source (i.e. free) DBMS that runs on
  Windows, MAC and UNIX platforms.
• Oracle
• A company that makes powerful DBMS.
• SQL Server.
• Microsofts DBMS, a version of this comes free
  with Visual Studio.

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Microsoft Access.

• Only ten users may access the database at a given
  time
• not good for building your multimillion pound
  online store
• However
• Most students are familiar with the application.
• It is part of the Microsoft Office
• It is easy to set up and use

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Data Aware Objects.

• Objects are used allow our programs to control
  computer technology.
• The email object
• allows us to create emails
• The SMTP client object
• allows us to control an SMTP server, i.e. send
  emails.
• The variable (object)
• allows us to store data in the RAM.
• Control objects
• allow us to set up regions of the screen so the
  screen so the user may interact with it.

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ADO.NET (Active Data Objects).

• Used to control databases.
• Problem!
• It is huge and complex and would need a year long
  course just to get to grips with it.

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The DatabaseTable Object.

• A custom object written for this module.
• Allows simple control of a database.
• Hides ADO.NET so you can get on with the task at
  hand.
• DatabaseTable acts as a kind of secretary. You
  send it a simple command and then it uses ADO.NET
  on your behalf to interact with the database.

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Four Things we want to do.

• Produce a list of records for searching or so
  that the user may see them all at once.
• Add a new record to the database.
• Edit an existing record in the database.
• Delete a record.

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Producing a List of Records.

• E.g. Hotmail

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Assuming we have the following data
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Giving us
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Tutorial Questions.

• Q1. What do the letters DBMS stand for?
• Q2. Declare a DatabaseTable object that connects
  to a database called email.mdb and a table
  called outbox.
• Q3. Given the following table
• Write a line of code that assigns the subject
  line of message four to a variable called Subject.

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Tutorial Questions.

• Q4. Write a line of code that assigns the count
  of records to a variable called RecordCount.
• Q5. Write a loop that adds the subject lines of
  each record to a list box called lstMessages.