Create composite keys

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The primary key of a fact table is usually a composite key made up of all or a subset of its foreign keys. The primary key in a fact table determines the uniqueness of each row. 

In some cases, a surrogate key can also act as the fact table’s primary key. This fact table’s surrogate key is typically an auto-incremental numeric field, commonly defined as an identity column. The main purpose of the fact table’s surrogate key is to ensure row uniqueness in situations where it is a business requirement to allow duplicate rows in your fact table.

Foreign keys in a fact table determine what dimensions have a direct relationship with the fact table. This is also referred to as the dimensionality of the table. The table’s dimensionality reflects the grain or granularity of the fact table.


Column types in fact table

 Primary key Column or columns that determine the uniqueness of the table.

 Foreign keys Columns with a value that references a primary key column of a dimension.

 Measures Columns with a value that contains quantifiable data, usually numeric, that can be aggregated.
Metadata Columns that track data lineage, auditing and other data warehouse processes.
Exam 70-767

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