Multiple Bridge tables to a single fact?
2 posters
Page 1 of 1
Multiple Bridge tables to a single fact?
Hi
We have had a design option proposed that has a single fact table, which has 2 bridge tables to multivalued dimensions.
Given that a bridge table changes the grain of the fact table to the level of the bridged multivalued dimension, I would not have thought it was possible to then join a second multivalued dimension to the fact using its own bridge table. Thoughts on this please?
We have had a design option proposed that has a single fact table, which has 2 bridge tables to multivalued dimensions.
Given that a bridge table changes the grain of the fact table to the level of the bridged multivalued dimension, I would not have thought it was possible to then join a second multivalued dimension to the fact using its own bridge table. Thoughts on this please?
Bumblebee- Posts : 3
Join date : 2015-03-04
Re: Multiple Bridge tables to a single fact?
Yes, you can combine multiple bridges in a query. However, unrestricted, you create a cartesian product. This may be significant depending on the cardinality of these relationships. You also need to include an allocation factor for each relationship to distribute measures to the new grain. Multiplying cumulative factors (from the multiple bridges, and provided it is stored as a value between 0..1) to properly allocate the cartesian product before summarization.
If you do allocation, be ready to support multiple allocation factors for different purposes. Allocations tend to be a hot topic among different departments.
If you do allocation, be ready to support multiple allocation factors for different purposes. Allocations tend to be a hot topic among different departments.
Similar topics
» Single fact table vs multiple fact tables - what is the right way in a dimensional model?
» context for multiple fact and bridge tables
» Multiple Fact Tables vs. Consolidated Fact Table
» Modelling question - Multiple fact tables with one to many relationships and querying from many fact tables
» Multiple Date Values for a Single Fact Row
» context for multiple fact and bridge tables
» Multiple Fact Tables vs. Consolidated Fact Table
» Modelling question - Multiple fact tables with one to many relationships and querying from many fact tables
» Multiple Date Values for a Single Fact Row
Page 1 of 1
Permissions in this forum:
You cannot reply to topics in this forum