Star Schemas issue fixes in Modelling of Microstartegy
Explanation | This schema is characterized by one lookup table per dimension, with base tables at the lowest level. This is the fastest way to set up a data warehouse: |
Problem | Double counting. According to the diagram above, a report that contains month and the a metric SUM(SALES_AMT) will go to the aggregate table and join to the column to retrieve the description from the table. Since the column is not unique in its lookup table, the results will appear duplicated. |
Recommendation | MicroStrategy engine is optimized to work with snowflake schemas, where each attribute level has a distinct lookup table. Star schemas are supported with restrictions, as long as fact tables are not at a higher level than the dimension tables to which they are joined. Consult the following MicroStrategy Knowledgebase document for further information.
KB19194 - Considerations for the use of star schemas with MicroStrategy SQL Generation Engine
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Workaround / Solution | If aggregate tables are needed, use one lookup table per attribute to avoid double counting. |
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