Dimension Table and Fact Table

Dimension Table vs Fact Table

Dimension table and fact table are mainly used in data warehousing. The fact table mainly consists of business facts and foreign keys that refer to primary keys in the dimension tables. A dimension table consists mainly of descriptive attributes that are textual fields.

Dimension tables provide descriptive or contextual information for the measurement of a fact table. On the other hand, fact tables provide the measurement of an enterprise.
A dimension table contains a surrogate key, natural key, and a set of attributes. On the contrary, a fact table contains a foreign key, measurements, and degenerated dimensions.

When comparing the size of the two tables, the fact table is bigger than the dimensional table. In a comparison table, more dimensions are presented than the fact tables. In a fact table, less numbers of facts are observed. In a dimension table, the values are text representations or numeric. In a fact table the values are in integer form or numeric.

A fact table normally contains two columns – one that contains the facts and the other foreign keys to the dimension table. Dimension tables are also called reference tables.

When dimension tables can be loaded directly, it is not possible with a fact table. In a fact table, the dimension table has to be loaded first. While loading the fact tables, one should have to look at the dimension table. This is because the fact table has measures, facts, and foreign keys that are the primary keys in the dimension table.

Summary:

1.The fact table mainly consists of business facts and foreign keys that refer to primary keys in the dimension tables. A dimension table consists mainly of descriptive attributes that are textual fields.
2.A dimension table contains a surrogate key, natural key, and a set of attributes. On the contrary, a fact table contains a foreign key, measurements, and degenerated dimensions.
3.Dimension tables provide descriptive or contextual information for the measurement of a fact table. On the other hand, fact tables provide the measurements of an enterprise.
4.When comparing the size of the two tables, a fact table is bigger than a dimensional table. In a comparison table, more dimensions are presented than the fact tables. In a fact table, less numbers of facts are observed.
5.The dimension table has to be loaded first. While loading the fact tables, one should have to look at the dimension table. This is because the fact table has measures, facts, and foreign keys that are the primary keys in the dimension table.

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