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This article introduces the knowledge of "what is OLAP". In the operation of actual cases, many people will encounter such a dilemma. Then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

# what is OLAP

OLAP (On-LineAnalysis Processing) online analysis and processing is a fast analysis technology for sharing multi-dimensional information; OLAP uses multi-dimensional database technology to enable users to observe data from different angles. OLAP is used to support complex analysis operations, focusing on decision support for managers, can meet the requirements of analysts to quickly and flexibly carry out complex queries of big data complex quantity, and present query results in an intuitive and easy-to-understand form to assist decision-making.

# related concepts

Dimension

It is a specific point of view for people to observe the data, and a set of attributes when considering the problem forms a dimension (such as time dimension, geography dimension, etc.).

Level (Level)

There can also be various descriptive aspects with different levels of detail (such as time dimension: date, month, quarter, year) from a particular angle (that is, a certain dimension) of the data. That is, the level of dimension.

Member (Member)

One value of a dimension is the description of the position of the data item in a dimension. ("a certain year, a certain month and a certain day" is a description of the position in the time dimension.

Metric (Measure)

The value of a multidimensional array, such as the salary of a certain month and day in a certain year.

Drilling (Drill-up and Drill-down)

Change the level of dimension, change the granularity of analysis. Drill-up generalizes low-level data to high-level summary data or reduced dimensions; drill-up, on the contrary, delves the summarized data into details, or adds new dimensions.

Slices and sections

It is concerned about the distribution of the measurement data on the remaining dimensions after the values are selected on some dimensions. If there are only two remaining dimensions, it is sliced; if there are three or more, it is sliced.

Rotation

Is the direction of transforming dimensions, that is, rearranging the placement of dimensions in a table (such as column interchange)

Star pattern

It consists of a fact table and a dimension table, which includes foreign keys and a measure of all the analysis dimensions. The dimension table corresponds to the perspective of each analysis, and contains description and classification information in addition to the primary key.

Snowflake model

Sometimes, the definition of dimension table will become complicated, for example, the product dimension should be divided according to the product category, some special goods should be divided into brands, and the methods of product brand and product category division are not the same. Therefore, a single dimension table is not an ideal solution and can be used in the following ways, and this data model is called the snowflake model.

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