Herring Ryan

A brief introduction to OLAP

OLAP models use a multidimensional architecture, allowing for complex analytical and ad-hoc queries with a rapid execution time. They borrow aspects of navigational databases and hierarchical databases that are faster than relational databases.

An example of a multi dimensional OLAP cube might be for Sales where the cube will have the dimensions Months, Years, Regions, Products and Measures.

Dimensions usually have one or more hierarchies, for example the Region dimension might have Wellington, Palmerston North, Taupo all rolling up into "Lower North Island". Viewing this consolidated element would give an aggregate total from all the low level regions. "Total North Island" would include all these regions, plus those from the "Upper North Island".

The Measures dimension would include elements such as "Sales Value", "Sales Qty" and "Cost of Sales".

The output of an OLAP query is typically displayed in a matrix (or pivot) format. Two of the dimensions form the rows and columns of the matrix while the user will choose one element (which may be consolidated) for each of the other dimensions.

To learn more about OLAP concepts contact Herring Ryan.