fact table typically has two types of columns: those that contain numeric facts (often called measurements) and those that are foreign keys to dimension tables.
A fact table contains either detail-level facts or facts that have been aggregated. Fact tables that contain aggregated facts are often called summary tables. A fact table usually contains facts with the same level of aggregation.
Though most facts are additive they can also be semi-additive or non-additive. Additive facts can be aggregated by simple arithmetical addition. A common example of this is sales. Non-additive facts cannot be added at all.
An example of this is averages. Semi-additive facts can be aggregated along some of the dimensions and not along others. An example of this is inventory levels where you cannot tell what a level means simply by looking at it.
Non additive facts are the facts that do not participate in arithmetic caliculations. for example in stock fact table there will be opening and closing balances along with qty sold and amt etc. but opening and closing balances were never used in arithmetic calculations.
