CS 395 Database Practicum C' Shilepsky

1
CS 395 Database PracticumC. Shilepsky

• Class 5, March 5, 2001

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Files for Class 5

• TestTimer.vbp
• Magnet.mdb (Access file)
• Magnet.vbp (VB project)
• bank.mdb for homework

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Adding a Timer

• Control the clock
• Properties
• Interval (in milliseconds)
• Enabled (whether it is operating
• Methods
• Timer (action to occur each interval)

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Database Access from VB

• VB can connect to a database.
• The default database is Access
• VB contains the Jet database engine and doesnt
  need Access to create and operate on .mdb
  (Access) files.
• Connection can be through a data control or by
  direct coding.

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Example (Magnet)

• Database Magnet.mdb.
• Open in Access
• View the table tblOrderMaster
• Fields fldOrderID, fldCustomerID, fldOrderDate,
  fldOrderCost, fld OrderSales
• VB Project Magnet.vbp
• One form frmOrder
• The bar at the bottom (data control) allows you
  to navigate through Magnet.mdb

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Data Control
(on the form)
(the database)
(on the form)
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Data Control

• Enables user to interface with database functions
  (to retrieve, update, navigate).
• Actually maps the db to VB controls on a form
• Data control is not visible, rather a conduit to
  the particular db.
• Runtime the data control establishes the
  connection to the database and mediates
  interactions.

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Bound Controls

• On a form
• Visible
• These display a field from the current db record
  or query.
• They are bound via the data control.

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Data Control for Magnet

• datOrderMaster
• Properties
• Caption--the name in the control
• Connect--the type of database (Access)
• DataBaseName--Magnet.mdb (you may need to update
  this for your location)
• RecordSource--the Access table that provides data
  to the VB form

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Bound Controls for Magnet

• Data control datOrderMaster is set up the link to
  the Access database
• txtOrderID,..,txtOrderCost now need to be bound
  to data fields in Magnet.mdb
• txtOrderID Properties
• DataSource (the control) datOrderMaster
• DataField (the element in the control)
  fldOrderID
• Note txtOrderProfit not bound to anything
• Changes in Access database reflected on the VB
  form and conversely

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Using the VB Data Form Wizard

• The Data Form Wizard automates building a simple
  form that connects to a database.
• How
• Start a blank project
• Under Project/Add Form select VB Data Form Wizard
• No profile
• Access database. Magnet.mdb
• Single Record
• Record Source tblOrderMaster
• Challenge what does the code mean?

12
Homework

• Build a front-end viewer for bank.db
• Include a data control and bound control for each
  field in the branch table.
• Note, the naming of tables and fields in bank.mdb
  do not match VB conventions (tblX, fldX)
• Do the same using the Data Wizard. We will go
  over its features and the code next class.
• Reference Rahmel, Teach Yourself Database
  Programming
• with VB 6 in 24 Hours, p.11-37.