Getting Started with IBM Data Studio for DB2

266 Getting Started with IBM Data Studio for DB2
Scalar functions are widely used in SQL statements to do processing of individual or
aggregate values. UDFs that receive multiple values as input and return a scalar value are
called aggregate functions.
Here is an example of using the built-in scalar function concat():
db2 => values CONCAT('Hello', ' World')
1
-----------
Hello World
1 record(s) selected.
You can use table functions in several different ways. You can use a table function to
operate (with SQL language) on data that is not stored in a database table, or even to
convert such data into a table. You can use them to read data from files, from the Web, or
from Lotus Notes databases, and return a result table. The information resulting from a
table function can be joined with information from other tables in the database, or from
other table functions.
9.2 Creating a user-defined function
Data Studio supports template based user-defined function creation. There are many
predefined routine templates that allow the user to create user-defined functions easily. A
routine template is a predefined text with some standard code, comments, best practices,
etc. that makes it easy for developers to start creating new user-defined functions.
To create a UDF, follow these steps:
1. Create a new data development project as you learned to do in Chapter 8. Name the
projectUDF Project.
2. Right-click on the User-Defined Functions folder under UDF Project, and select New ->
User-Defined Function as shown in Figure 9.1.