OLE Automation Objects in Transact-SQL
Transact-SQL includes several system stored procedures that allow OLE Automation objects to be referenced in Transact-SQL batches, stored procedures, and triggers. These system stored procedures run as extended stored procedures, and the OLE Automation objects that are executed through the stored procedures run in the Microsoft® SQL Server™ 2000 address space in the same way that an extended stored procedure runs.
The OLE Automation stored procedures allow Transact-SQL batches to reference SQL DMO objects and custom OLE Automation objects, such as objects that expose the IDispatch interface. A custom in-process OLE server created using Microsoft Visual Basic® must have an error handler (specified with the On Error GoTo statement) for the Class_Initialize and Class_Terminate subroutines. The error handlers prevent unhandled errors from occurring in these subroutines. Unhandled errors in the Class_Initialize and Class_Terminate subroutines can cause unpredictable errors, such as an SQL Server access violation. Error handlers for other subroutines are also recommended.
The first step when using an OLE Automation object in Transact-SQL is to call the sp_OACreate system stored procedure to create an instance of the object in the SQL Server address space.
After an instance of the object has been created, call these stored procedures to work with the properties, methods, and error information related to the object:
- sp_OAGetProperty obtains the value of a property.
- sp_OASetProperty sets the value of a property.
- sp_OAMethod calls a method.
- sp_OAGetErrorInfo obtains the most recent error information.
When there is no more need for the object, call sp_OADestroy to deallocate the instance of the object created with sp_OACreate.
OLE Automation objects return data through property values and methods. sp_OAGetProperty and sp_OAMethod return these data values in the form of a result set.
The scope of an OLE Automation object is a batch. All references to the object must be contained in a single batch, stored procedure, or trigger.
When referencing objects, the SQL Server OLE Automation objects support traversing the object to other objects it contains. For example, when using the SQL-DMO SQLServer object, references can be made to databases and tables contained on that server. For more information, see Object Hierarchy Syntax.