Slides from a client-server data access session that both Toni and I gave several times.

1. E-CS
Client Server Data Access
Techniques with Visual
FoxPro
Mike Feltman
F1 Technologies

2. Who Am I?
• mfeltman@f1tech.com
• F1 Technologies Partner
• Visual FoxExpress Developer
• Former Fox Software Employee
• Application Programmer

3. Our Goals
• Provide you with an overview of each of the
data access techniques
• Make you aware of the pros and cons of the
various techniques
• Equip you with the information necessary to
make an informed choice of data access
technique.

4. Agenda
• Overview of Various Data Access Techniques
• Evaluation Categories
– Ease of Use
– Performance and Scalability
– Maintainability
– Flexibility
– Security Concerns/Issues
• Mixing and Matching Techniques

5. The Data Access Methods
• Remote Views
• Dynamic SQL Pass-Through
• Stored Procedures
• CursorAdapter
• ADO
• XML

6. Ease of Use
• UI and Tool Support
• Data Binding
• Normalcy
• Completeness
• Plays Well With Others
• Distribution Difficulties

7. Remote Views
• UI & Tools Support
– View Builder, GenDBC
– eView & View Editor
– xCase
– DBCX
• Data Binding
– Full Support in Data Environment
• Normalcy
– Most similar to tables

8. Remote Views
• Completeness
– Full Language Support in VFP
– Limited Access to Back-end Features
• Plays Well With Others
– Very well, Can share connections
• Distribution
– DBC Distribution

9. Dynamic SPT – Ease of Use
• UI and Tool Support
– None Native, Some 3rd Party
• Data Binding
– Manual or Tricks
• Normalcy
– Requires More Code to work like a View
(CursorSetProp())

10. Dynamic SPT – Ease of Use
• Completeness
– Access to full back-end
• Plays well with others
– Very well except for ADO
• Distribution Issues
– None

11. Stored Procedures – Ease of Use
• UI and Tool Support
– None in VFP
– DataClas
– Enterprise Manager and QueryAnalyzer
– Mike Levy’s Classes from various conferences

12. Stored Procedures – Ease of Use
• Completeness
– Access to everything the back-end has to offer
– Great for Multiple and/or Complex Statements
• Distribution Difficulties
– Must update stored procedures
– Code Conflict Resolution

13. CursorAdapter with ODBC – Ease of
Use
• Similar to Remote Views
• UI and Tool Support
– CursorAdapter & DE Builder
– 3rd Party Tools
• Normalcy
– Just like a Table or View

14. CursorAdapter with ODBC – Ease of
Use
• Completeness
– More code than remote views, less than other
techniques
• Plays Well With Others
– Easiest

15. CursorAdapter with ADO/OLEDB –
Ease of Use
• Similar to CursorAdapter with ODBC
• Plays Well With Others
– Cannot share connection with other data access
strategies
• Distribution Concerns
– MDAC

16. Performance and Scalability
• The differences between various techniques are
generally minor.
• Server, Workstation & LAN/WAN performance and
scalability must ALL be taken into account
• Size (& Contents) Matters
• Query optimization in SQL Server is much different
than in VFP. Syntax vs. Content-based optimization.

17. Performance and Scalability
• Results can vary widely for the same tests.
• Those with much more experience than me with
large databases (million rows+) all swear Stored
Procedures produce the best performance.
• Microsoft tends to get very angry at those who
publish SQL Server benchmarks.

18. Maintainability
• Code Requirements
– How much code?
• Maintenance Points
– How many?
– Easy to find and work with?
• Tools
– Are there any?
• Schema Changes
– What happens when schema changes?

19. Maintainability - Remote Views
– Code Requirements
• Little
– Maintenance Points
• Primarily the views themselves
• Custom classes

20. Maintainability - Remote Views
– Tools
• View Designer, eView, ViewEditor, xCase, GenDBC
– Schema Changes
• Use xCase
• Unit test remote views

21. Maintainability - Dynamic SPT
– Code Requirements
• One good base class
• App specific subclasses
– Maintenance Points
• Custom Class Code

22. Maintainability - Dynamic SPT
– Tools
• None
– Schema Changes
• Maybe do nothing
• Unit test data access code

23. Maintainability - Stored
Procedures
– Code Requirements
• VFP – One good set of classes
• 4 or more Procedures for basically every table
– Maintenance Points
• Custom classes
• Actual Stored Procedures

24. Maintainability - Stored
Procedures
– Tools
• None for VFP
• DataClas, 3rd Party
– Schema Changes
• All Procedures
• Unit Test all Stored Procedures

25. Maintainability - CursorAdapters
– Code Requirements
• One good base class
– Maintenance Points
• Individual subclasses
– Tools
• 3rd party, DE and CA Builder
– Schema Changes
• Modify CA properties
• Unit test all cursor adapters

26. Flexibility
• Remote Views
– Inflexible without other techniques
• Dynamic SPT
– Highly flexible with custom classes, but overly
difficult to write

27. Flexibility
• Stored Procedures
– Very Flexible
– Much like Dynamic SQL Pass-Through
• Cursor Adapter
– Most Flexible – mix & match with all techniques
– Native class provides appropriate locations for
customization

28. Security
• Stored Procedures – Execute Rights on Stored
Procedures Only
• All Others – Provide direct rights to update
tables or views
• DSN Based Connection vs. Connection String
is more important
• Use Application Roles

29. Mixing and Matching
• CURSORSETPROP()
– Make SPT Cursor Updatable
– Load data into remote view
• USE … CONNSTRING (handle)
• CursorAdapter.CursorAttach
• SQLSTRINGCONNECT()

30. Summary
• Be Informed!
• It is Not an “All or Nothing” Situation
• Choose the Best Approach for the Application
• Mix and Match When Necessary.

31. Thank you!