Extraction, Transformation, and Loading - Data Warehouse Systems: Design and Implementation - page 294

Shippers Orders Employees

ShipperID
CompanyName
Phone

OrderID
CustomerID
EmployeeID
OrderDate
RequiredDate
ShippedDate (0,1)
ShipVia
Freight
ShipName
ShipAddress
ShipCity
ShipRegion (0,1)
ShipPostalCode (0,1)
ShipCountry

EmployeeID
FirstName
LastName
Title
TitleOfCourtesy
BirthDate
HireDate
Address
City
Region (0,1)
PostalCode
Country
HomePhone
Extension
Photo (0,1)
Notes (0,1)
PhotoPath (0,1)
ReportsTo (0,1)

Customers

CustomerID
CompanyName
ContactName
ContactTitle
Address
City
Region (0,1)
PostalCode (0,1)
Country
Phone
Fax (0,1)

OrderDetails

OrderID
ProductID
UnitPrice
Quantity
Discount

Suppliers

Employee
Territories
EmployeeID
TerritoryID

SupplierID
CompanyName
ContactName
ContactTitle
Address
City
Region (0,1)
PostalCode
Country
Phone
Fax (0,1)
Homepage (0,1)

Territories

Products

TerritoryID
TerritoryDescription
RegionID

ProductID
ProductName
QuantityPerUnit
UnitPrice
UnitsInStock
UnitsOnOrder
ReorderLevel
Discontinued
SupplierID
CategoryID

Regions

Categories

RegionID
RegionDescription

CategoryID
CategoryName
Description
Picture

Fig. 8.14 Schema of the Northwind operational database (repeated from Fig. 2.4 )

Figure 8.18 provides a general overview of the whole ETL process.
The figure shows the control tasks needed to perform the transformation
from the operational database and the additional files presented above and
the loading of the transformed data into the data warehouse. We can see that
the process starts with a start event, followed by activities (with subprocesses)
that can be performed in parallel (represented by a splitting parallel gateway)
which populate the dimension hierarchies. Finally, a parallel merging gateway
synchronizes the flow, meaning that the loading of the Sales fact table