Question: Write a short note on Fact Constellation

Mumbai University > Computer Engineering > sem 8> data warehouse and mining

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mumbai university • 254 views
modified 6 weeks ago  • written 7 weeks ago by gravatar for Ankit Pandey Ankit Pandey60

Fact Constellation

  • As its name implies, it is shaped like a constellation of stars (i.c., star schemas).
  • This schema is more complex than star or snowflake varieties, which is due to the fact that it contains multiple fact tables.
  • This allows dimension tables to be shared amongst the fact tables.
  • A schema of this type should only be used for applications that need a high level of sophistication.
  • For each star schema or snowflake schema it is possible to construct a fact constellation schema.
  • That solution is very flexible, however it may be hard to manage and support.
  • The main disadvantage of the fact constellation schema is a more complicated design because many variants of aggregation must be considered.
  • In a fact constellation schema, different fact tables are explicitly assigned to the dimensions, which are for given facts relevant.
  • This may be useful in cases when some facts are associated with a given dimension level and other facts with a deeper dimension level.
  • Use of that model should be reasonable when for example, there is a sales fact table (with details down to the exact date and invoice header id) and a fact table with sales forecast which is calculated based on month, client id and product id.
  • In that case using two different fact tables on a different level of grouping is realized through a fact constellation model.

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written 6 weeks ago by gravatar for Ankit Pandey Ankit Pandey60
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