Advanced Visual Basic

1
Advanced Visual Basic

• Database Objects

2
The Microsoft Data Access Model

• Preferred Method
• Universal Data Access
• OLE DB Data Driver
• ActiveX Data Objects (ADO) - Interface
• Other Methods
• Open Database Connectivity (ODBC)
• Remote Data Objects (RDO)
• Data Access Objects (DAO)

3
Connecting to the Data

• Define the connection
• Location
• Provider
• Example
• Location c\data\mydata.mdb
• Provider Jet 4.0 (Access 2000 Database)

4
Storing Connection Information

• Data Sources Applet in the Control Panel
• Hard Coded into Application
• Universal Data Link File (UDF)
• Data connection information is stored in a file
• Easy to manage
• Easy to change

5
Visual Basic Tools

• Data Environment Designer
• ADO Data Control
• ADO Class
• ADO directly in code

6
Our Method

• ADO Data Aware Class (p. 531)
• UDL (p. 503)

7
Other Information

• Cursor Types
• Record Locking Methods
• Terms

8
Cursor Types

• adOpenDynamic
• Dynamic cursor. Additions, changes, and deletions
  by other users are visible, and all types of
  movement through the recordset are allowed,
  except for bookmarks, if the provider doesn't
  support them.
• adOpenStatic
• Static cursor. A static copy of a set of records
  that you can use to find data or generate
  reports. Additions, changes, or deletions by
  other users are not visible.

9
Record Locking Methods

• adLockReadOnly
• adLockPessimistic
• Pessimistic locking, record by record. The
  provider does what is necessary to ensure
  successful editing of the records, usually by
  locking records at the data source immediately
  upon editing. You can add, delete, and change
  records.
• adLockOptimistic
• Optimistic locking, record by record. The
  provider uses optimistic locking, locking records
  only when you call the Update method. You can
  add, delete, and change records.

10
Terms

• Microsoft Jet 4.0
• Database access engine that allows us to use MS
  Access Database files
• MDAC
• Drivers that allow us to access different types
  of data sources including Access Database through
  Jet
• ADO
• Interfaces that we can connect to using VB.