Data engineering and IT
Foreign key
- Data engineering and IT
Definition
A column in one table whose values must match the primary key of another table, so the two tables stay correctly linked.
Example
In Raket Parts B.V. data, sales_orders.customer_ref is a foreign key to customers.customer_ref. All 7,235 orders point to one of the 436 customers, with no orphan orders. A database can enforce this, refusing an order for a customer who does not exist.
Raket Parts B.V. is a fictional company created for Insyt.
See how it works
The matching values link the two tables. Some systems enforce referential integrity; other analytical stores may not.
Check your understanding
Common mistake: A matching column name does not by itself establish a valid or enforced foreign-key relationship.
What can happen if an order references a customer that does not exist?
Show explanation
It creates an orphan reference unless an enforced constraint prevents the write.
For your role
Choose your role to see what this term means in your work.
Why it matters
It keeps related data consistent and tells you which columns to join on.
Where it is used
Database design and data model relationships. Used by data engineers, BI developers and data analysts.