data-warehouse - 加法、半加法和非加法测量有什么区别

Question

我在网上搜索了数据仓库中加法、半加法和非加法度量之间的区别。我找到了一些结果，但我很难理解这些差异，因为它们不是一个例子。您能否通过示例向我更多地解释加法、半加法和非加法措施之间的区别。

Answer 1

The numeric measures in a fact table fall into three categories. The most flexible and useful facts are fully additive; additive measures can be summed across any of the dimensions associated with the fact table.

完全可加度量的一个示例是销售额(从商店购买)。您可以添加每小时销售额以获取一天、一周、一个月、一个季度或一年的销售额。您可以添加跨商店或跨地区的销售额。

Semi-additive measures can be summed across some dimensions, but not all; checking account or savings account balance amounts are common semi-additive facts.

您可以从交易文件中重新创建余额金额，但添加 10 月、11 月和 12 月(跨时间维度)的余额金额没有任何意义。

Finally, some measures are completely non-additive, such as ratios. A good approach for non-additive facts is, where possible, to store the fully additive components of the non-additive measure and sum these components into the final answer set.

最后，您计算最终的非可加性事实。

强调，通常情况下，非添加剂是平均值、百分比和比率，对它们进行额外的聚合是无关紧要的(例如，将一个产品的 2 个销售比率相加根本没有意义)，
因此，非附加事实不应存储在事实表中，并且通常会在事实表中对附加事实进行操作。

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