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Fact & Dimension tables

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Fact and Dimension table what does it mean? How do we classify which is fact and dimension table? Where do we use these. These are some of the most common questions that pop up when we hear dimension and fact table.

Going by book, Fact and Dimension table in technical perspective is defined as follows

The fact table contains business facts (or measures), and foreign keys which refer to candidate keys (normally primary keys) in the dimension tables.

A dimension table is a table in a star schema of a data warehouse. A dimension table stores attributes, or dimensions, that describe the objects in a fact table.

Not let’s dig into this we have basically two schemas Star and Snow Flake schema

In Star schema  a fact table is surrounded by dimension tables. In Snow flake schema we have again Fact table in the center of schema  surrounded by dimension tables, however in here the dimension tables can have their own child tables.

facts correspond to events, dimensions correspond to people, items, or other objects. For example, in the retail scenario, Purchases, returns and calls are facts. On the other hand, customers, employees, items and stores are dimensions .

  

 
                                               

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