Friday, August 16, 2013

Standalone & Embeded Filter

Stand alone Filter: Use a stand-alone calculation when you want to reuse the expression. You can apply a stand-alone calculation to one or more dimensions or query subjects to provide calculated data to a report, or include it in a package to make it available to your users. By moving a stand-alone calculation or a shortcut to it into a folder, you can better organize your model objects. Embeded fileter: Use an embedded calculation when you want to use a calculation with only one dimension or query subject. You can create an embedded calculation when modifying a relational data source query subject, model query subject, or dimension. other way we say that... Creating and using the filter inside a query subject while building it. This filter can't be reused in any case. (private variable) Stand alone: Creating a filter out side of a query subject, using the wizard. This can be reused. (Public variable)
FACTLESS FACT :
factless fact table is “a fact table that has no facts but captures the many-to-many relationship between dimension keys.”
Confirmed Dimension: A conformed dimension is a set of data attributes that have been physically referenced in multiple database tables using the same key value to refer to the same structure, attributes, domain values, definitions and concepts. A conformed dimension cuts across many facts. Dimensions are conformed when they are either exactly the same (including keys) or one is a perfect subset of the other. Most important, the row headers produced in two different answer sets from the same conformed dimension(s) must be able to match perfectly. Conformed dimensions are either identical or strict mathematical subsets of the most granular, detailed dimension. Dimension tables are not conformed if the attributes are labeled differently or contain different values. Conformed dimensions come in several different flavors. At the most basic level, conformed dimensions mean exactly the same thing with every possible fact table to which they are joined. The date dimension table connected to the sales facts is identical to the date dimension connected to the inventory facts.
Junk Dimension A Junk Dimension is a dimension table consisting of attributes that do not belong in the fact table or in any of the existing dimension tables. The nature of these attributes is usually text or various flags, e.g. non-generic comments or just simple yes/no or true/false indicators. These kinds of attributes are typically remaining when all the obvious dimensions in the business process have been identified and thus the designer is faced with the challenge of where to put these attributes that do not belong in the other dimensions.
Role Playing dimension : Dimensions are often recycled for multiple applications within the same database. For instance, a "Date" dimension can be used for "Date of Sale", as well as "Date of Delivery", or "Date of Hire". This is often referred to as a "role-playing dimension".
Slowly changing dimension SCD The most common types are I, II, and III. Type I This methodology overwrites old with new data, and therefore does not track historical data. The disadvantage of the Type I method is that there is no history in the data warehouse. It has the advantage however that it's easy to maintain. If you have calculated an aggregate table summarizing facts by state, it will need to be recalculated when the Supplier_State is changed. Type II This method tracks historical data by creating multiple records for a given natural key in the dimensional tables with separate surrogate keys and/or different version numbers. Unlimited history is preserved for each insert. Type III This method tracks changes using separate columns and preserves limited history. The Type III preserves limited history as it's limited to the number of columns designated for storing historical data. The original table structure in Type I and Type II is the same but Type III adds additional columns.