Heard the term OLAP a lot? It stands for online analytical processing. You would use it to analyze multidimensional data. OLAP is part of business intelligence. For example, it can be used for business reporting of sales. It can also be used for data mining. The data is organized in cubes, not tables. This data is queried and becomes parts of reports. There are not as many transactions involved. The database does not have to be huge like a data warehouse.

There are three main operations in OLAP:
  1. Consolidation
  2. Drill down
  3. Slicing and dicing
Consolidation, also know as roll up, is aggregation of data. Drill down is the opposite. It is going into the details. Slicing and dicing let's you view data from different viewpoints. Those viewpoints are called dimensions.

There is a certain term in OLAP called the OLAP Cube. It is also known as a multidimensional cube or hypercube. It contains numeric facts (called measures) categorized by dimensions. This cube is created from data warehouse schemas. The speed in accessing the cube is from the aggregation of data. For some complex queries, accessing data can be 1000 times faster than querying a normal database.

There are different types of popular OLAP systems:
The MOLAP is the multidimensional one. This is the classic type of OLAP. Data is in special array storage hardware. It is fast on queries, and requires less disk space. Loading data into it can be time consuming though. ROLAP is a relational database OLAP. Slicing and dicing translate into WHERE clauses of SQL statements in ROLAP. You can ask this system any question since it has all the non-aggregated data. HOLAP is a hybrid between MOLAP and HOLAP.