1. MIS 451 Building Business Intelligence Systems
Logical Design (4)

3. D4: Conformed Dimension
A conformed dimension table is a dimension table shared by fact tables.
Ex: PRODUCT dimension table is shared by two fact tables – SALESFACT and PROCOST.
A conformed dimension table should mean the same thing with every fact table to which it is joined.
D: refers to special considerations for dimension tables or special types of dimension tables

4. D4: Conformed Dimension
Conformed dimension tables connect separate star schemas into an enterprise star schema.
Support drill across queries on star schema

5. D5: Role-playing Dimension
Role-playing dimension is a dimension which plays several simultaneous roles when used with a fact table.
In the following star schema, time dimension plays two different roles – ORDERDATE and DELIVERYDATE.

6. D5: Role-playing Dimension
Although ORDERDATE and DELIVERYDATE have exactly the same table structure, they need to be treated as different tables.
SALEFACT (CUSTOMER_KEY, PRODUCT_KEY, ORDERDATE_KEY, DELIVERYDATE_KEY, QUANTITY, SALES)
ORDERDATE (ORDERDATE_KEY, ODATE, DAY_OF_WEEK, DAY_OF_MONTH)
DELIVERYDATE (DELIVERYDATE_KEY, DDATE, DAY_OF_WEEK, DAY_OF_MONTH)
Query: List sales of products ordered on Wednesday and delivered on Friday
Select sum(sales)
From SALEFACT S, ORDERDATE O, DELIVERYDATE D
Where S.ORDERDATE_KEY = O. ORDERDATE_KEY AND
S. DELIVERYDATE_KEY = D. DELIVERYDATE_KEY AND
O.DAY_OF_WEEK = 3 AND
D.DAY_OF_WEEK = 5

7. D5: Role-playing Dimension
If we replace ORDERDATE and DELIVERYDATE with one time dimension table SDATE, we get,
SALEFACT (CUSTOMER_KEY, PRODUCT_KEY, ORDERDATE_KEY, DELIVERYDATE_KEY, QUANTITY, SALES)
SDATE (SDATEID, SDATE, DAY_OF_WEEK, DAY_OF_MONTH)
Note: ORDERDATE_KEY and DELIVERYDATE_KEY in SALEFACT table are foreign keys refer to SDATEID in SDATE table.
Query: List total sales ordered on Wednesday and delivered on Friday
Select sum(sales)
From SALEFACT S, SDATE SD
Where S.ORDERDATE_KEY = SD.SDATEID AND
S.DELIVERYDATE_KEY = SD.SDATEID AND
SD.DAY_OF_WEEK = 3 AND
SD.DAY_OF_WEEK = 5
This query will return nothing!

8. F2: Types of Fact Attributes
Additive fact attributes can be added along any dimension.

9. F2: Types of Fact Attributes
Non-additive fact attributes cannot be added along any dimension.

10. F2: Types of Fact Attributes
Semi-additive fact attributes can be added along some dimensions.

11. F3: Factless Fact Table
Factless fact table is a fact table that contains only warehouse keys without any fact attributes.
Factless fact table is useful for event tracking, such as tracking student class attendance event.

12. F3: Factless Fact Table

13. F3: Factless Fact Table
Instead of sum function used in common fact tables, query on factless fact tables use count function
How may courses did student Mark take on 01/01/99?
Select count(course_key)
From Attendance A, Attend_time AT, Student S, Course C
Where A.Time_key = AT.Time_key AND
S.Student_key = A.Student_key AND
S.SNAME = ‘Mark’ AND
AT.Date = ’01/01/99’

14. Readings:
Chapter 3: p49 – p52
Chapter 5
Chapter 10