ch3 - Ch 3 Inventory 1 Topics include: value chain...

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Unformatted text preview: Ch 3 Inventory 1 Topics include: value chain motivation for conformed dimensions fact tables o transaction o periodic snapshot o accumulating snapshot bus architecture o the matrix o conformed dimensions o conformed facts Case Study Chapter 3 uses inventory as the basis of the case study, introduces the concept of a value chain . We begin modeling store inventory: The business process: retail store inventory Grain of the fact table: daily inventory by product at each individual store The dimensions: date, product, store (no promotion dimension) The facts: quantity on hand The schema for the case study. Next, we discuss the fact table and the characteristics of its attributes. Facts Metrics: quantity on hand There is one row for each day a count is made for each product and each store Recall measures can be described as additive, non-additive, semi-additive "quantity on hand" is a semi-additive fact; it can be summed meaningfully across any dimension except one:________________. store inventory snapshot fact quantity on hand Next, we look at the internal structure of a row in the fact table. Ch 3 Inventory 2 Physical layout of fact table The physical fact table has measures, foreign keys, and degenerate dimensions. Each foreign key is a reference to a row of a dimension table. A degenerate dimension is an operational number, for example: a sale transaction number. (There is no DD in this fact table.) Logical table store inventory snapshot fact quantity on hand Physical table store inventory snapshot fact date key (FK) product key (FK) store key (FK) quantity on hand There are three foreign keys comprising the primary key for the fact table Sample rows date key product key store key quantity on hand 1 1 15 66 1 2 10 97 1 3 7 95 ... ... ... ... 2 1 16 87 2 2 20 94 2 3 15 44 2 4 9 34 ... ... ... ... Sample store inventory MS Access database Periodic Snapshots The store inventory snapshot fact table is a periodic snapshot Each day (or similar period) it is updated Ch 3 Inventory 3 It is not transaction oriented (as in Ch 2) In Ch 2 we saw a transaction fact table It is a common type of fact table - there are three types Enhancing the fact table The text discusses the inclusion of more facts: quantity sold, dollar value at cost, dollar value at latest...
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This note was uploaded on 02/17/2010 for the course ACS ACS-3911 taught by Professor Chen during the Spring '10 term at Windsor.

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ch3 - Ch 3 Inventory 1 Topics include: value chain...

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