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Adjoining Dimension Columns: Example<br />
Consider adjoining the following dimension columns to the POS<br />
Transaction Fact table (Slide pg 27) to give POS ADC<br />
Date.Qtr in a 3 year history of transactions, 12 values, as POS.D_Qtr<br />
Store.Nation in multi-national sales with 9 nations, as POS.S_Nation<br />
Product.Dept, with 18 Departments in the business, POS.P_Dept<br />
Promotion.MediaType, with 9 such types, as POS.PR_Type<br />
Number of cells added to make POS ADC is: 12*9*18*9 = 17,496<br />
May see skew in count of rows in cell combinations of dimension<br />
column values: say smallest cells size is 1/2 size of largest<br />
We want each cell to contain at least 1 MB so sequential scan<br />
swamps seek time between cells: We should be safe assuming<br />
35000 cells of equal size: implies we need 70 GB in POS ADC<br />
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