CHAPTER 8More Slow Change Techniques
A crucial part of star schema design is determining how changes to source data will be reflected in dimension tables. The change response pattern for each dimension attribute in the star schema must be carefully matched to business requirements. Most requirements can be satisfied by employing the techniques introduced in Chapter 3:
• Type 1 is used when the history of the data element is not significant. When a source data element changes, the corresponding dimension attribute is overwritten. This causes previously recorded facts to become associated with the changed value. No trace of the old value is left behind.
• Type 2 is used when it is important to preserve the historic context of facts with respect ...