Описание тега fact
A fact or fact table is the central table in a Star or Snowflake schema of a data warehouse. A fact table stores quantitative information for analysis and is often denormalized. It measures the business operations in the organization. It is included in every data warehouse or data mart.
Facts are the measurements that result from a business process event and are almost always numeric. A single fact table rows has a one-to-one relationship to a measurement event as described by the fact table's grain. Fact table corresponds to a physical observable event.
Within a fact table, only fact consistent with the decraled grain are allowed. The fact table work with dimension tables. The fact table holds the ways in which the fact table data can be analyzed. There are two type of columns in there - foreign key columns for join with the dimensions and the measures columns, containing the data analyzed.
Example
In retail sales transaction, the quantity of a product sold and its extended price are good facts. Store manager's salary is disallowed in the fact table.
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