Principle: create fact tables with the most granular data possible to support analysis of the business process.
In Data warehousing grain refers to the level of detail available in a given fact table as well as to the level of detail provided by a star schema.
It is usually given as the number of records per key within the table. In general, the grain of the fact table is the grain of the star schema.
Facts: Facts must be consistent with the grain.all facts are at a uniform grain.
- Watch for facts of mixed granularity
- Total sales for day & montly total
Dimensions: each dimension associated with fact table must take on a single value for each fact row.
- Each dimension attribute must take on one value.
No comments:
Post a Comment