Difference between star and snowflake schemas

Difference between star and snowflake schemas

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Star schema: A highly de-normalized technique. A star schema has one fact table and is associated with numerous dimensions table and depicts a star. Snow flake schema: The normalized principles applied star schema is known as Snow flake schema. A dimension table can be associated with sub dimension table i.e. the dimension tables can be further broken down to sub dimensions. Differences: A dimension table will not have parent table in star schema, whereas snow flake schemas have one or more parent tables. The dimensional table itself consists of hierarchies of dimensions in star schema, where as hierarchies are split into different tables in snow flake schema. The drilling down data from top most hierarchies to the lowermost hierarchies can be done.

level of Granularity of a fact table, The granularity is the lowest level of information stored in the fact table. The depth of data level is known as granularity. In date dimension the level could be year, month, quarter, period, week, day of granularity.