ISCG 6425 Data Warehousing Staging Tables

4.2 ETL Process Northwind1 DataWarehouse Northwind2 STAGING AREA Different Data Sources

4.3 Why we need Staging? 1.Don’t disturb the operation of the OLTP 2.Don’t harm our existing Datawarehouse 3.Make some transformations with data 4.The ability to reload if something went wrong

4.4 Don’t harm OLTP Northwind1 Northwind2 Take all the tables needed from the OLTP Sometimes the whole source database can be copied Staging Area OLTP (source data)

4.5 Do Transformations Example: Remove Null Value Orders Table With Null value Staging Area BufferOrders Table No null value

4.6 IS NULL Function Orders Table With Null value BufferOrders Table No null value 2. SQL INSERT INTO BufferOrders (OrderID,CustomerID,OrderDate,ShippedDate) SELECT OrderID,CustomerID,OrderDate, IS NULL (ShippedDate, ‘ ’) FROM Orders 1. SQL CREATE BufferOrders (Same as Orders table) Enter some date here to replace Null

4.7 NEXT DO Merge Using Your Staging Table Have Fun!