Chapter 9, Performing Advanced Operations with Databases

Pop quiz – implementing a Type III SCD in PDI

Q1

2 (1) is not a valid option. The Dimension L/U by itself is not prepared to maintain the previous value and the current value in the same record automatically. There are very few things you cannot do with PDI if you have to work with data, so (3) is out of discussion. The right answer is (2). With a Database lookup to get the current value stored in the dimension. If there is no data in the dimension table, the lookup fails and returns null; that is not a problem. After that, you compare the found data with the new one and set the proper values for the dimension columns. Then, you load the dimension either with a Combination L/U or with a Dimension lookup, just as you do for a regular Type I SCD. It's worth saying that type III SCD are used rather infrequently and cannot always be automated. Sometimes they are used to represent human-applied changes and the implementation...