My first Publication Agile-Data-Warehouse-Design-eBook | Page 193

Dimensional Design Patterns for People and Organizations, Products and Services
173
Figure 6-4
Swappable
dimensions
Swappable Dimension Consequences
Swappable dimensions increase the number of database objects that need to be
maintained. You should only create them as physical tables if they improve per-
formance. For databases that support variable length column types, sparsely
populated exclusive attributes can take up very little space and cause less of a
performance issue. In which case, swappable dimensions that are needed only to
improve usability can be implemented as database views.
Customer Relationships: Embedded Whos
The stakeholder’s specification for the CUSTOMER dimension, in Figure 6-5,
contains attributes that relate each business customer to two other whos: an em-
ployee playing the role of ACCOUNT MANAGER [HV], and another customer
playing the role of PARENT COMPANY [CV]. Both of these embedded whos need
to be fully described with HV or CV attributes for reporting purposes.
Who dimensions
can often contain
references to other
whos that need to
be fully described
Figure 6-5
CUSTOMER
dimension with
embedded who
attributes