Dw design fact_tables_types_6

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Tipos de tablas de hechos

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Dw design fact_tables_types_6

  1. 1. DATA WAREHOUSINGMulti DimensionalData Modeling.Fact Table Types
  2. 2. 2
  3. 3.  Transaction  Track processes at discrete points in time when they occur  Periodic snapshot  is a fact table that records activity during a repeating predictable time period, like the monthly summary of a bank account  Accumulating snapshot  A snapshot of the most recent state of something and therefore the dimensional foreign keys and the facts are, in general, over-written as time progresses3
  4. 4.  Transaction-grained fact tables are often richly dimensional and usually have only a single fact (the amount of the transaction).4
  5. 5.  Periodic snapshot records are generally repeated each reporting period as long as the thing being measured (like the account) is in existence.5
  6. 6.  Periodic snapshots are appropriate for long running processes that extend over many reporting periods.6
  7. 7.  Accumulating snapshots, are used for short processes that have a definite beginning and end, such as an order being filled.7
  8. 8.  For an order, we would usually make a record for each line on the order, and we would revisit the record making updates as the order progressed through the pipeline8
  9. 9.  The simplest implementation of an accumulating snapshot does not give you intermediate points in the history of, for example, an order.9
  10. 10.  Accumulating snapshots typically have multiple dates in the fact table representing the major milestones of the process. However, just because a fact table has several dates doesn’t dictate that it is an accumulating snapshot.  The primary differentiator of an accumulating snapshot is that we typically revisit the fact rows as activity takes place.10
  11. 11.  The Data Warehouse Toolkit.Second Edition.The Complete Guide to Dimensional Modeling.Ralph Kimball.Margy Ross

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