1. Visual Basic Database Access
BICS546

2. Microsoft Universal Data Access
OLE DB: The OLE database protocol
Allows a program to access information in any type of data source, and it is the basis for ADO.
Data provider: databases, spreadsheets, etc.
ADO: ActiveX Data Objects
An Interface for OLE DB.
Allow programmers to use a standard set of objects to refer to any OLE DB data source.
ODBC: Open Database Connectivity
A driver manager
Used for relational databases

3. Program
ActiveX Data Objects
OLE DB
Provider
OLE DB
Provider
ODBC
Data Source
ODBC
Data Source

4. Using ODBC Three types of data source names
User DSN: usable only by you and only on the machine currently using.
System DSN: Any one using the machine can use.
File DSN: Can be copied and used by other computers with the same driver installed.

5. Visual Basic Database Tools
Visual Data Manager
Data Environments
Data Views
Data Report Designer
Data Projects

6. Visual Data Manager Add-Ins/Visual Data Manager
Supports: Access, dBase, FoxPro, Paradox, ODBC, Text files.
Creating new database
Managing existing database
Query Builder, Form Wizard
DAO

7. Data Environments Project/More ActiveX Designer/Data Environment
Data Environments are designed to be the basis of design-time and run-time data access. They make data available to any forms and modules in your application.

8. Data Environments at Design Time
Right Click Connection1
Click Properties to set up database connection
Click Add Command to choose record source.
Drag and drop fields from Command1 to form. Text box properties:
Data Source: Data Environment1
Data Member: Command1 (Note: Data environment can support many command objects)
Data Field

9. Data Environments at Run Time
Access command object’s Recordset object and Recordset object’s methods.
Recordset’s name: rs+command name.
Ex. rsCommand1
Properties:
EOF, BOF, RecordCount
Methods:
MoveFirst, MoveLast, MoveNext, MovePrevious

10. Data Environment Code Example
DataEnvironment1.rsCommand1.MoveNext
IF DataEnvironment1.rsCommand1.EOF THEN
DataEnvironment1.rsCommand1.MoveLast
END IF

11. Data Views View/Data View Window
An overview of the database objects you have in a project, such as Data Environments, connections, data links.

12. Data Report Designer Project/Add Data Report
Features of Data Report Designer
Drag and Drop fields from the Data Environment to report detail section. The DataMember and DataField properties of the text box are automatically set.
Drag and Drop the Command object (Must make sure the DataSOurce and DataMember properties of the DataReport are set properly).

13. Data Report Code Example
‘To preview report
DataReport1.Show
‘To print
DataReport.PrintReport

14. Data Projects
VB projects come with built-in Data Environments and Data Report Designer.

15. Using Databases in VB Three VB database objects:
DAO, RDO, ADO
Two ways to work with these objects:
VB Data controls, data-bound controls
Programming objects

16. DAO Support the Jet database DAO data control Database property
RecordSource property: tables, queries, SQL statement
RecordSet Type Property: Table, Dynaset, Snapshot
Able to connect to data sources such as dBase, text files, and Excel spreadsheet.

17. ADO Data Control Project/Components/Microsoft ADO 6.0
Double Click ADO to insert ADO
Right Click and select ADODC Properties
General : Source of Connection
RecordSource:
1 – adCmdText: SQL statement
2 – adCmdTable: Table in the database
4 - adCmdStoredProc

18. ADO Properties BOF Action, EOF Action
Command TimeOut: Amount of time in seconds the ADO control will allow for commands to be executed on the server.
ConnectionString
CursorLocation: server site, client site
CursorType
MaxRecords: 0 means no limit.
RecordSource

19. Cursor Type
Forward Only: Can only move forward through the recordset (can only MoveNext). Use the least amount of system resources.
Static: Can navigate in both directions. Unable to see changes made by other users.
Keyset: Can see changes made by other users (except insertions).
Dynamic: Use most of resources, and can see all changes made by other users.

20. Cursor Lock Type ReadOnly
Optimistic: Does not lock the file until updates are actually applied.
BatchOptimistic: All changes be submitted at one time.
Pessimistic: Lock the table the entire time that the recordset is open.

21. Cursor Mode Property Determines the access rights of the user. Read
Write
ReadWrite
ShareDenyRead: Deny other from opening connections with read permissions.
ShareDenyWrite
ShareExclusive
ShareDenyNone: Prevent others from opening conections with any permissions.