OLAP cube

An OLAP cube is a special way to organize information, like a data cube, to help people analyze large amounts of data quickly. It uses a multi-dimensional array of data, which means the information is arranged in many different directions, making it easier to see patterns and relationships.

OLAP, which stands for online analytical processing, is a computer-based technique that helps people dig deeper into data to find useful insights. By using an OLAP cube, businesses and researchers can ask complex questions and get answers much faster than with regular databases. This tool is very important for making smart decisions based on data.

Terminology

A cube is like a special way to organize information, similar to how a spreadsheet works but in more than two directions. Imagine a company wants to look at its money details by what they sell, when they sell it, and where they sell it. These different ways of looking at the data are called dimensions.

Each spot in the cube holds a number that shows something important about the business, like how much they sold or spent. This helps people see patterns and make better decisions.

Hierarchy

The elements of a dimension can be organized as a hierarchy, which means they have parent-child relationships. Usually, a parent shows a total of its children. These parents can also be grouped together as children of another parent.

For example, May 2005 is part of the Second Quarter of 2005, which is part of the Year 2005. In the same way, cities belong to larger regions, products belong to product groups, and individual expenses belong to types of spending.

Operations

When we think of data as a cube with different parts, it becomes easier to analyze. Users can move around the cube by choosing what to look at, which is called "slice and dice." Common ways to work with the cube include slicing, dicing, drilling down/up, rolling up, and pivoting.

Slice means picking a part of the cube by choosing one value for a part of it, making a new, smaller cube.

Dice lets the user pick specific values from several parts of the cube to create a smaller cube.

Drill Down/Up lets the user move between general and detailed levels of data.

Roll-up means adding up data along a part of the cube, like finding totals.

Pivot lets the user turn the cube to see different sides of the data. For example, cities could be shown up and down, and products side to side, and after turning, products could be shown up and down and time side to side.

Mathematical definition

In database theory, an OLAP cube is a way to organize information from databases. Think of it like a box where each side shows different details. For example, you might have three main things you're looking at—like the type of product, the store location, and the time of year. These three things act like the sides of the box.

Because we usually look at things on paper or screens, which are flat, we often take "slices" of this box to see it better. This means we focus on just two of the three things at a time. The result looks like a table where one side lists the products and the other side lists the stores, and where they meet, you see numbers that tell you something important about that product in that store. This helps us understand big sets of data more easily.