Students often blur the concepts of snowflakes, outriggers, and bridges. In this Design Tip, I’ll try to reduce the confusion surrounding these embellishments to the standard dimensional model. When a dimension table is snowflaked, the redundant many-to-one attributes are removed into separate dimension tables. For example, instead of collapsing hierarchical rollups such as brand and category into columns […]
Kimball Design Tips
It’s surprising the number of DW/BI teams that confine the responsibility for designing dimensional models to a single data modeler or perhaps a small team of dedicated data modelers. This is clearly shortsighted. The best dimensional models result from a collaborative team effort. No single individual is likely to have the detailed knowledge of the business requirements and the […]
Ralph’s first article on data warehousing appeared in 1995. During the subsequent 13 years, we’ve written hundreds of articles and Design Tips, as well as published seven books. Remarkably, the concepts that Ralph introduced in the 1990s have withstood the test of time and remain relevant today. However, some of our vocabulary has evolved slightly over the years. This […]
Delivering consistent data is like reaching the top of Mount Everest for most data warehouse initiatives, and data stewards are the climbers who fearlessly strive toward that goal. Achieving data consistency is a critical objective for most DW/BI programs. Establishing responsibility for data quality and integrity can be extremely difficult in many organizations. Most operational systems effectively capture key […]
Many transaction processing systems consist of a transaction header “parent” with multiple line item “children.” Regardless of your industry, you can probably identify source systems in your organization with this basic structure. When it’s time to model this data for DW/BI, many designers merely reproduce these familiar operational header and line constructs in the dimensional world. In this Design […]
Conformed dimensions are the glue that ties together your enterprise data warehouse. To facilitate and manage the conforming process, we have identified two additional fundamental responsibilities for the DW/BI team: the dimension manager and fact provider. Typically these functions are performed by the ETL team working closely with the data stewardship organization. The dimension manager is a centralized […]
With their graphically appealing user interfaces, dashboards and their scorecard cousins are demo superstars. Dashboards have really grabbed the attention of senior management since they closely align with the way these people operate. What’s not to like about the promise of performance feedback on every customer or supplier facing process in the organization at a glance. It’s no […]
Childhood guessing games sometimes rely on the distinction of “person, place or thing” for early mystery-solving clues. Some modelers use these same characterizations in their data models by creating abstract person, place and/or thing (typically referred to as product) tables. While generalized tables appeal to the purist in all of us and may provide flexibility and reusability advantages for […]
Meaningless integer keys, otherwise known as surrogate keys, are commonly used as primary keys for dimension tables in data warehouse designs. Our students frequently ask us – what about fact tables? Should a unique surrogate key be assigned for every row in a fact table? Although for the logical design of a fact table, the answer is no, […]
Your ETL system may need to process late arriving dimension data for a variety of reasons. This design tip discusses the scenario where the entire dimension row routinely arrives late, perhaps well after impacted fact rows have been loaded. For example, a new employee may be eligible for healthcare insurance coverage beginning with their first day on the […]