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GeekInterview.com > Interview Questions > Data Warehousing > Basics
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Question: What are non-additive facts
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| July 07, 2005 20:29:38 |
#2 |
| Kenny |
Member Since: Visitor Total Comments: N/A |
RE: What are non-additive facts
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fact table typically has two types of columns: those that contain numeric facts (often called measurements), and those that are foreign keys to dimension tables.
A fact table contains either detail-level facts or facts that have been aggregated. Fact tables that contain aggregated facts are often called summary tables. A fact table usually contains facts with the same level of aggregation.
Though most facts are additive, they can also be semi-additive or non-additive. Additive facts can be aggregated by simple arithmetical addition. A common example of this is sales. Non-additive facts cannot be added at all.
An example of this is averages. Semi-additive facts can be aggregated along some of the dimensions and not along others. An example of this is inventory levels, where you cannot tell what a level means simply by looking at it. |
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