Database Connect: Execute common SQL queries for different databases

This class provides a database abstraction layer to execute common SQL queries in different database types.

There is factory class that can create objects of different classes to access different types of databases. Currently there are classes to access Interbase, Microsoft SQL server, MySQL and PostgreSQL.

These database access classes implement a common interface for executing SELECT, INSERT, UPDATE and DELETE queries.

The SELECT query results are stored in a protected array class variable. The base class implements functions to retrieve data from the query results.