Dimension Table
Dimension tables
contain attributes that describe fact records in the fact table. Some of these
attributes provide descriptive information; others are used to specify how fact
table data should be summarized to provide useful information to the analyst.
The dimension table rows provide meaning to the rows in the
fact table. Each dimension table describes a particular business entity or aspect of the fact
table entries. Typical dimension tables include time, geography, customers, and
products. Dimension tables should consist of three types of columns. The first
is a newly generated primary key (PK) for each row in the dimension table. The
second is the original PK from the source system, and the third group consists
of any number of additional columns that further describe the business entity. Columns in a dimension table can be used to
categorize the information into hierarchical levels.
The following diagram illustrates a subsection
of the AdvantureWorkDW sample
database, in which the FactResellerSales
fact table is related to two dimension tables, DimReseller and DimPromotion.
The ResellerKey Column in the FactResellerSales fact table defines a
foreign key relationship to the ResellerKey
primary key column in the DimReseller
dimension table. Similarly, the PromotionKey
column in the FactResellerSales fact
table defines a foreign key relationship to the PromotionKey primary key column in the DimPromotion dimension table.
![DimensionTable.bmp]( "DimensionTable")