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COM-based Data Sources

Crystal Reports provides direct access or native drivers for some databases. These drivers are written specifically for a particular database and are often the best choice. However, because hundreds of types of databases exist, Crystal Decisions can't possibly write direct access drivers for all of them. So often, users turn to using standard data access layers such as ODBC or OLEDB to connect to their databases. Often, the vendor of a database will provide an ODBC driver or OLEDB provider so that other applications can access the vendor's database. Sometimes though, even this is not enough. Customers have data that they would like to report off of that is not accessible by any Crystal Reports data source driver or via ODBC or OLEDB. To this, customers often turn to the COM Data Source driver or the Java Data Source driver. This section describes the COM version of the driver, but much of the theory applies to the Java Data Source driver as well.

COM, or the Component Object Model, is a Microsoft-based technology for software component development. It's the underlying technology that runs things such as Visual Basic and Active Server Pages. A COM object is a piece of code that adheres to the COM specification and is easily used by other components, both inside a single application or between disparate applications.



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