Getting Started with IBM Data Studio for DB2

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Chapter 9 – Developing user-defined functions
In this chapter, you will learn how to develop user-defined functions (UDFs) by using Data
Studio.
9.1 User-defined functions: The big picture
Like stored procedures, UDFs encapsulate reusable code. Because UDFs can be used in
SQL statements, they let you extend the SQL language with your own logic. For example,
you might want to create a function that encapsulates the logic to calculate a tax value in
your country when a source value is given as input, or you can create a function that
extracts information from an XML document and returns it in a tabular form that can be
used to perform a JOIN with another table. UDFs provide a very flexible way to extend your
application.
The supported languages for UDFs that are developed using Data Studio are: SQL, and
PL/SQL. The DB2 server supports other languages for UDFs, such as Java and C++, but
those are not supported in Data Studio.
Note:
Although you can use Data Studio to create PL/SQL functions for DB2 projects, PL/SQL
support is not available in DB2 Express-C, which is the edition of DB2 used for the
examples in this book. If you wish to develop PL/SQL functions, you’ll need to upgrade
to a different edition of DB2 that contains PL/SQL support.
UDFs developed in Data Studio can have one of the following return types:
Scalar: UDFs that accept one or more scalar values as input parameters and return a
scalar value as result. Examples of such functions include the built-in length(), and
concat() functions.
Table: UDFs that accept individual scalar values as parameters and return a table to
the SQL statement which references it. You can reference table functions in the FROM
clause of a SELECT SQL statement.