MSBI -- SSAS -- Part-6

Dimension Table and Types

 Dimension Table:

The table which stores Master data OR Organizational level data is known as Dimension table.

Types of Dimension Table:

                               Following are the types of Dimension Tables available in Data warehousing.

1.     SCD (Slowly Changing Dimension)

2.     Conformed Dimension

3.     Roll Playing Dimension

4.     Junk Dimension

5.     Bridge Dimension

6.     Degenerative Dimensions

1.   SCD (Slowly Changing Dimension)

                             As we know that, the dimension table data will not change frequently. But after some time the dimension data also be changes, during that time we need to capture the changes and update into the target dimension table, this is known as SCD.

2.   Conformed Dimension

                                                    In a Dimension Modeling Schema, if one Dimension table is shared by more than one Fact Table, such a type of Dimension is known as Conformed Dimension.

3.   Roll Playing Dimension

                                                    In a Dimension Modeling Schema, if there are more number of references to the Fact Table from a particular Dimension Table, Such type of Dimension Table is known as Roll Playing Dimension Table.

4.   Junk Dimension

                                        In a Dimension Modeling Schema, if the Dimension Table maintains Boolean kind of information like Yes/No or True/False. Such kind of Dimension table is known as Junk Dimension.

5.   Bridge Dimension

                                     In a Dimension Modelling Schema, The Bridge table is an intermediate table which is used to handle Many-to-Many relationships.

Many - to - Many Relationship:

Explanation:             

                         There is a possibility of more than one reason to cancel an order and also one reason will be responsible to cancel more orders. Such kind of relationship is called as Many-to-Many Relationship. To handle these kind of situations we have to use Bridge Table.                   

6.   Degenerative Dimensions

                                                            It is a kind of Dimension Table which is not physically present in the database. With one Fact table attribute, we can get all the descriptive information from other Dimension Tables.
For an Example:

In the above table, by using INV001 Invoice Number we can get all the Dimension informations like Product , Order , Date and Customer Details.