You can import a mapplet to create a custom generation rule. You must mark at least one input and one output column as required. Use custom rules to generate data for string, numeric, and date data types.
For example, an EMPLOYEES table contains columns for first name and last name. You create a custom generation rule to combine the first and last name of an employee to generate the full name.
You can also create custom rule with mapplets when you want to use PowerCenter transformations, such as an SQL transformation or a Stored Procedure transformation. You can also use custom mapplets when you need to use the logic to generate records or generate output with the user defined procedure.