Keys (Primary Key , Foreign Key, Surrogate Key, Composite Key, Natural Key)

In data warehousing, keys play a crucial role in structuring and organizing data within the data warehouse environment. They are used to establish relationships between different tables and ensure data integrity.

 

 

Primary Key

A primary key is a unique identifier for each record (row) in a table.

It ensures that each record in the table can be uniquely identified and distinguishes it from other records.

Primary keys are used to enforce entity integrity and prevent duplicate records.

In dimensional modeling, primary keys are often used in dimension tables to uniquely identify each dimension member.

 

Foreign Key

A foreign key is a column or set of columns in a table that establishes a relationship with the primary key in another table.

It represents the "many" side of a one-to-many or many-to-one relationship between tables.

Foreign keys ensure referential integrity by enforcing that values in the foreign key column(s) must match values in the corresponding primary key column(s) in the related table.

In dimensional modeling, foreign keys are commonly used in fact tables to establish relationships with dimension tables.

 

Surrogate Key

A surrogate key is a system-generated unique identifier assigned to each record in a table.

It is often used as a substitute for natural keys (keys derived from business data) to simplify data integration and ensure data consistency.

Surrogate keys have no business meaning and are solely used for internal database processing.

They provide a stable and reliable means of uniquely identifying records, even if natural keys change over time or are not available

 

Composite Key

A composite key is a combination of two or more columns that together uniquely identify each record in a table.

It is used when no single column can uniquely identify records, but a combination of columns does.

Composite keys are commonly used in junction tables or bridge tables that represent many-to-many relationships between entities.

 

Natural Key

A natural key is a column or set of columns in a table that uniquely identifies records based on their inherent business characteristics.

Natural keys are derived from business data and have meaning outside of the database.

They are often used when there is a clear and stable identifier available in the source system, such as product codes, customer IDs, or employee numbers.