There is no great variety of functions in this area. Data Services encourages you to communicate with database objects and control the flow of data within a dataflow.
You will learn a little more about the functions here.
First, let's look at the key_generation() function. This is the function the can be called only from the dataflow (when used in column mapping), so we are not interested in it at this point as we cannot use it in the Data Services scripts.
This function is actually similar to the Key_Generation transform object that can be used as part of a dataflow as well, and it is used to lookup the highest key value from a table column and generate the next one. This is often used to populate the key column of the new record with the unique values before inserting this record to a target table. We will take a closer look at the Key_Generation transform in the upcoming chapters.