File Processing

1. File Processing • Concepts • Field – combination of 1 or more characters that is the smallest unit of data to be accessed • Record – group of related fields • File – group of related records

2. Databases • Data organized in a manner that allows access, retrieval and use of that data • DBMS (data base management system) • Software that can create, add, delete, manipulate and retrieve data from a database.

3. Why DBMS? • Helps to eliminate data redundancy • Registrar – student files with your name address, etc. • Financial Aid may duplicate some of the data • Can be helped with centralized files and file design • Inconsistent data • Change it in 1 file was it changed in another • Low programmer productivity • DBMS can do some of the tasks that a programmer has to do with a file processing system. • Ex. Referential integrity rules (can’t delete a master record for a sales person until the customers assigned to that sales person have been deleted or updated)

4. Customer Data

5. Database concepts • Columns of a table (fields or attributes) • Rows of table ( records) • Database can have multiple tables • Relational databases have a fields or fields in one table that relates to a primary key in another table • Primary key – field or fields that uniquely identify a record • Foreign key – field or fields in one table that relates to a primary key in another

6. Accessing Databases in Visual Basic • To access a database you use a database protocol • DAO – Data Access Object • RDO – Remote Data Object • ADO – ActiveX Data Object

7. Ways to Access Databases in VB • Two ways to work with the protocols • Use built in Visual Basic Controls • use special controls to connect to and move through databases • Add the data control to a form and then set properties, methods and events • Simple to use but limited in what you can do. • Reference a library of programming objects that let you handle the protocols in code

8. Each data control supports SQL • SQL – structured query language • Standard language that can add, delete, modify and retrieve data as well create a database

9. DAO • Early versions of VB did not support databases • By ver 4.0 Access type databases were supported – Access uses the jet database engine • DAO was created to support the Jet database and database programming took off with VB • There was also a DAO object library created

10. RDO • Originally DBMS operated on stand alone computers, but now multiple computers may share data across a network • Microsoft came up with a standard named ODBC (open database connectivity) • ODBC sets up protocols to work with non-Microsoft databases such as Oracle • RDO allows direct access to ODBC connections( all data does not follow ODBC specs)

11. Universal Data Access • Universal Data Access • a strategy by Microsoft to provide access to all types of data without requiring it to be stored in a standard format • Types of data include databases, files, Internet data • To implement this model an interface named COM( Component Object Modules) • Protocol by which different objects communicate

12. OLE DB and ADO • A standard interface for accessing information stored in many formats • In Visual Basic you access OLD DB through ActiveX Data Objects (ADO) • Controls

13. Intrinsic and ActiveX Controls • Intrinsic – • ex. Text box (not unique to VB but available in all windows programs through the windows API) Code to implement one is embedded in the .exe • ActiveX • code to implement it is stored in a separate file .OCX • File must reside on computer with your VB .exe • ActiveX control is independent of VB and can be used in other languages