EmployeeID Name Title ManagerID
1 Torrey CEO
2 Hailey Admin Assistant 1
3 Molly VP Sales 1
4 Donald VP Human Resources 1
5 Hannah Director 3
6 Yoshi Director 3
7 Raghu Director 4
8 Mario Team Leader 7
9 Benny Benefits Admin 8
10 Patty Payroll Clerk 8
Table 3-2 The Organizational Chart in a Relational Table, Showing that the ManagerID
Is Tied to the EmployeeID.
C h a p t e r 3 : D a t a W a r e h o u s i n g a n d B u s i n e s s I n t e l l i g e n c e 41
can be summed by any dimension and provide a valid value. Other facts, such as
inventory levels, are semi-additive, meaning they cannot simply be summed across
all dimensions. The ending inventory for the first quarter cannot be added to the
ending inventory for the second quarter to give a valid inventory level for the first
half of the year. Instead, an average can be used, or simply the ending inventory for
the second quarter.
Facts, also called measures, reside in a fact table. The fact table is actually fully
normalized by nature, unlike the denormalized dimension tables. Typically, dimension
tables have single-field primary keys, often of an integer data type. Each fact represents
a unique combination of items for the lowest level of detail for each dimension.
As an example, assume three simple dimensions: Time, Product, and Customer.
The Time dimension goes to the Day level, the Product dimension goes to the SKU
level, and the Customer dimension goes to the Customer level.
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