Application Development Guide

Description

After a preliminary discussion on the interface between DB2 and a UDF, the remaining discussion concerns how you implement UDFs. The information on writing the UDF emphasizes the presence or absence of a scratchpad as one of the primary considerations.

Some general considerations in using this section are:

• Important material on defining and using UDFs is presented in User-Defined Functions (UDFs), and is not repeated here. This discussion concentrates on how you implement a UDF.

• To implement an external UDF written in C, C++ or Java, you must perform the following steps:
  • Write the UDF
  • Compile the UDF
  • Link the UDF
  • Register the UDF with a CREATE FUNCTION statement
  • Test and debug the UDF

  You can find information on compiling and linking UDFs in the Application Building Guide.

• You can invoke your UDF using OLE (Object Linking and Embedding) as described in Writing OLE Automation UDFs.

• You can define an OLE DB table function, which is a function that returns a table from an OLE DB data source, with just a CREATE FUNCTION statement. For more information on OLE DB table functions, see OLE DB Table Functions.

Note that a sourced UDF, which is different from an external UDF, does not require an implementation in the form of a separate piece of code. Such a UDF uses the same implementation as its source function, along with many of its other attributes.

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