Fact Table

            Fact Tables:

 A fact table contains composite keys (More than one key) where each candidate key is a foreign key to the dimension table.

 A fact table contains facts. In DWH, facts are generally numeric.

 A measure is a numeric attribute of a fact, representing the performance or behavior of the business relative to dimensions.

 A fact table contains the fact information at the lowest level granularity.

 The level at which fact information stores in a fact table is called as Fact Granularity or Grain of fact.

 A fact table can contain fact information either in 1NF or 2NF or 3NF. (NF: Normalization Form).

 To provide the meaningful business context to the facts design the dimension tables with a de-normalized business information.

2.         Types of Fact Tables:

                    I. Additive Fact table:

 A fact which can be summed up for any of the dimensions available in the fact table is called as Additive fact.

                  II.  Semi Additive Fact table:

 A fact which can be summed up for few dimensions but not for all the dimensions present in the fact table.

                III.  Non Additive Fact table:

 A fact which cannot be summed up for any of the dimensions available in the fact table.

               IV.    Fact less Fact Table:

 A fact which contains only Keys but not measures.

3.       Types of Facts:

                    I. Accumulative Fact Table:

 Generally these fact tables describe what has happened over the period of time. A cumulative fact table contains Additive or Semi additive facts. Ex: Transactional fact table, Orders fact table.

                  II. Snap shot Fact Table:

 This type of fact table describes the status of things at a particular instant of the time.