I have some entities in my Data Warehouse:
Person - with attributes personId, dateFrom, dateTo, and others those can be changed, e.g. last name, birth date and so on - slowly changing dimension
Document - documentId, number, type
Address - addressId, city, street, house, flat
The relations between (Person and Document) is One-To-Many and (Person and Address) is Many-To-Many.
My target is to create history fact table that can answer us following questions:
- What persons with what documents lived at defined address on defined date?
2, What history of residents does defined address have on defined interval of time?
This is not only for what DW is designed, but I think it is the hardest thing in DW's design.
For example, Miss Brown with personId=1, documents with documentId=1 and documentId=2 had been lived at address with addressId=1 since 01/01/2005 to 02/02/2010 and then moved to addressId=2 where has been lived since 02/03/2010 to current date (NULL?). But she had changed last name to Mrs Green since 04/05/2006 and her first document with documentId=1 to documentId=3 since 06/07/2007. Mr Black with personId=2, documentId=4 has been lived at addressId=1 since 02/03/2010 to current date.
The expected result on our query for question 2 where addressId=1, and time interval is since 01/01/2000 to now, must be like:
Rows:
last_name="Brown", documentId=1, dateFrom=01/01/2005, dateTo=04/04/2006
last_name="Brown", documentId=2, dateFrom=01/01/2005, dateTo=04/04/2006
last_name="Green", documentId=1, dateFrom=04/05/2006, dateTo=06/06/2007
last_name="Green", documentId=2, dateFrom=04/05/2006, dateTo=06/06/2007
last_name="Green", documentId=2, dateFrom=06/07/2007, dateTo=02/01/2010
last_name="Green", documentId=3, dateFrom=06/07/2007, dateTo=02/01/2010
last_name="Blac